Ink-jet recording apparatus and method using asynchronous masks

ABSTRACT

Random masks each having a given size and defining a random array of non-record pixel locations and record pixel locations are placed in association with record areas in mask registers. Using the placed masks, record data is thinned-out and supplied to a recording head. An image is then recorded. Thus, since thinning-out masks do not have periodicity, any inherent density nonuniformity loses periodicity. Consequently, high-definition images can be produced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording apparatus and method, ormore particularly, to an ink-jet recording apparatus and method forrecording by discharging ink from a recording head.

2. Description of the Related Art

Recording apparatuses such as printers, copying machines, and facsimilemachines are designed to record images formed with dot patterns onrecording materials such as paper or plastic film according to imageinformation.

When the recording apparatuses are classified in terms of recordingmodes, they are of an ink-jet type, a wire-dot type, a thermal type, anda laser beam type. The ink-jet type (ink-jet recording apparatus) isdesigned to effect recording by discharging ink (recording agent)droplets through ink-jet outlets in a recording head and fusing the inkdroplets onto a recording member.

In recent years, numerous recording apparatuses have been put to use.These recording apparatuses are being demanded to offer high recordingspeeds, high resolution, high image quality, and low noise. The ink-jetrecording apparatus is a recording apparatus capable of meeting thesedemands. The ink-jet recording apparatus effects recording bydischarging ink from a recording head. Stabilization of ink dischargingand quantity (volume) of discharged ink is therefore essential tosatisfy the above demands.

The ink-jet recording apparatus has a facility for stabilizing inkdischarging. Nevertheless, definition in recorded images depends largelyon the performance of an individual recording head. A very smalldifference of a recording head from others occurring in the process ofmanufacturing recording heads; such as, a difference in the shape ofeach ink-discharging outlet (port, orifice) of a recording head or adifference in performance of an electro-thermal converter (dischargeheater) affects a quantity of discharged ink or a discharge direction.Consequently, nonuniformity of density occurs in a finalized image, thusdeteriorating image definition.

An example of the foregoing problem will be described in conjunctionwith FIGS. 11-a-11-c and 12-a-12-c. In FIG. 11-a, 1101 denotes amultiple-nozzle recording head or multi-head. For simple illustration,the multi-head shall include eight nozzles 1102. Reference numeral 1103denotes ink droplets discharged by the multiple nozzles 1102. Normally,it is ideal that ink is discharged with equal quantities of dischargedink in the same direction. If this ink discharging is carried out, asshown in FIG. 11-b, dots of the same size are printed on paper toproduce a uniform image unaffected with nonuniformity of density (11-c).

In practice, however, as described previously, nozzles differ from oneanother. If printing is executed as described above with the nozzlesleft unchanged, as shown in FIG. 12-a, sizes and orientations of inkdroplets discharged by the nozzles differ from one another. The inkdroplets are shot at paper as shown in FIG. 12-b. As illustrated, ablank space appears at regular intervals in a main scanning direction ofa recording head because ink does not occupy a pixel 100%. Otherwise,dots overlap enormously, or a white band (stripe) runs as shown in thecenter of FIG. 12-b. Thus-printed dots result in the densitydistribution shown in FIG. 12-c along the nozzle array. As a result,these phenomena are perceived as nonuniformity of density by normalhuman eyes.

A method described in, for example, Japanese Patent Laid-Open No.60-107975 has been devised as a solution of the nonuniformity ofdensity. The method will be described in conjunction with FIGS.13-a-13-c and 14-a-14-c. According to the method, a multi-head 2001 isscanned three times in order to furnish a print area shown in FIGS. 11-band 12-b. A unit-area of four pixels is furnished by making two passes.Eight nozzles of the multi-head are grouped into four upper nozzles andfour lower nozzles. A dot printed by one nozzle during one scan is basedon defined image data that has been thinned out according to a certainimage data array so as to be about half in amount. Another dot is thenprinted based on the remaining half of the image data during the secondscan. Thus, printing is completed for the unit area of four pixels. Theforegoing recording method is referred to as a multi-pass recordingmethod.

When the multi-pass recording method is adopted, even if a multi-headsimilar to that shown in FIG. 12-a is employed, since influencesinherent to the nozzles upon a print image are halved, a printed imageappears as shown in FIG. 13-b. A black stripe and a white stripe shownin FIG. 12-b become inconspicuous. The nonuniformity of density shown inFIG. 12-c is considerably alleviated as shown in FIG. 13-c.

When the above recording is carried out, image data is grouped into twocomplementary portions to be assigned to the first and second scansaccording to a predetermined array. The image data array (thinning-outpattern) is usually, as shown in FIG. 14-a, a checker pattern in whichimage data is allocated to every other pixel location lengthwise andsideways.

Printing of a unit print area (of four pixels deep) is thereforecompleted by performing the first scan during which a checker pattern isprinted and the second scan during which an inverse-checker pattern isprinted.

Electric control for the foregoing thinned-out printing is illustratedin FIGS. 15 and 16. When print data Si is placed in an 8-bit shiftregister in response to a print data synchronizing clock CLK and thensignals BEI1*, BEI2*, BEI3*, and BEI4* are turned on, in a head unit 28a transistor array 26 is driven so that a heater 27 generates heat.Thus, printing is effected. Herein, the asterisk * indicates that thesignal is low active. A signal LATCH* is a control signal for latchingprint data. A signal CARESI* is a reset signal for clearing a latch 25.Every heating is initiated with a Heat Trigger signal. A pulse generator23 outputs the signals BEI1*, BEI2*, BEI3*, and BEI4*. These signals maysometimes be output with time lags between adjoining ones. Herein, theyare supposed to be output simultaneously.

For thinning out, a flip-flop 22 shown in FIG. 15 is triggered with theHeat Trigger signal so that signals (for example, the signals BEI1* andBEI3*) to be masked are alternately changed at every heating. Inreality, the signals to be masked are changed when an output signal DATAENB of the flip-flop 22 is driven high or low according to a timingchart shown in FIG. 16. With the Heat Trigger signal, the signals BEI1*,BEI2*, BEI3*, and BEI4* are driven low. Respective nozzles are heated.Dotted lines in FIG. 16 indicate masking durations which occur in linewith the cycle time of the signal DATAENB. Signals EVEN and ODD are usedfor initialization of a mask. When printing is to be performed using achecker-pattern mask, the signal EVEN is fed prior to printing of oneline. The flip-flop 22 is then pre-set, whereby printing based on achecker-pattern mask is enabled. For a line on which printing is to beperformed using an inverse-checker pattern mask, the signal ODD is fedto pre-set the flip-flop 22. The signals BEI2* and BEI4* are turned onearlier, whereby printing based on an inverse-checker pattern mask isenabled.

FIGS. 14-a, 14-b, and 14-c show how recording of a certain area iscompleted by applying checker-pattern and inverse-checker pattern masksusing a multi-head having eight nozzles as that shown in FIG. 13-a.First, during the first scan, four lower nozzles are used to create achecker pattern (hatched circles) (FIG. 14-a). Next, during the secondscan, paper is fed by a quantity correspondent with a depth of fourpixels (half of a head length). An inverse-checker pattern (whitecircles) is then created (FIG. 14-b). During the third scan, the paperis fed by a quantity correspondent with a depth of four pixels (half ofthe head length) again. A checker pattern is then created (FIG. 14-c).

As mentioned above, paper feed is performed in units of four pixels, andchecker-pattern and inverse-checker pattern masks are used alternately.A record area of four pixels deep is thus produced with each scan. Asdescribed above, two types of nozzles are used for the same area inorder to complete printing of the area. This results in a high-qualityimage unaffected with density nonuniformity. However, even when theforegoing multi-pass recording is adopted, the density nonuniformity maynot be eliminated depending on a duty ratio. Especially in half-tonerecording, new density nonuniformity may be identified. The phenomenonwill be described below.

In general, image data to be recorded in a certain area and received bya printer is regularly formatted as an array. A recording apparatusstocks or stores a certain amount of data in buffers, and applies a newmask having the aforesaid checker or inverse checker pattern (imagearray pattern) to the data. When the associated pixel locations in thedata and mask are turned on, the associated pixels are printed.

FIGS. 17 to 19 explain the above recording procedure. In FIG. 17, 1710denotes data having been arrayed and placed in a buffer. Referencenumeral 1720 denotes a checker-pattern mask indicating locations ofpixels allowed to be printed during the first pass. Numeral 1730 denotesan inverse-checker pattern mask indicating locations of pixels allowedto be printed during the second pass. Numerals 1740 and 1750 areillustrations showing pixels to be printed during the first and secondpasses respectively.

In FIG. 17, arrayed data is stocked in a buffer for 25% of a certainarea. The data is usually such print data that is scattered to thegreatest extent in an effort to keep the density in the certain areauniform. The fashion of arraying image data depends on what kind of areagray scale is employed for image data processing to be performed beforethe image data is transferred to a printer. Numeral 1710 denotes anexample of a data array of 25% image data. When the data is printed byapplying the masks 1720 and 1730, pixels representing exact halves ofthe original data are recorded as shown in the illustrations 1740 and1750 after the first and second passes respectively.

However, as shown in FIG. 18, when 50% image data comes in, it is quiteprobable that data 1810 dispersed to the greatest extent may beconsistent with a checker pattern mask 1820 or an inverse-checkerpattern mask 1830.

When such an event occurs, printing of all the image data is completedafter the first pass (1840). No recording is therefore performed duringthe second pass (1850). That is to say, the same nozzles are responsiblefor all the print data 1810. An adverse influence derived from thedifferences of the nozzles from one another is reflected as densitynonuniformity. The fundamental object of the aforesaid divisionrecording is not accomplished.

FIG. 19 shows printed states of arrayed image data offering a higherduty ratio than those shown in FIGS. 17 and 18. As apparent from FIG.19, the number of printed pixels differs considerably between the firstand second passes. Nonuniformity of density which is suppressed at ahigh duty ratio close to 100% recurs at a low duty ratio below 50%.

Consideration will be taken with regard to printing on transparent filmunder these circumstances. Printing is completed by making the first andsecond passes so that as many adjoining dots as possible will not beprinted simultaneously. This is intended to prevent occurrence ofbeading. Nevertheless, the aforesaid print state ensues. This means thatthe advantage of division printing is not exerted because of acombination of a specific dither pattern and a print pattern. Beading isconspicuous in an area of a produced image corresponding to the combinedportion of the patterns. If gradation is printed, a quite unpleasanttexture appears in the area of the image.

In FIG. 14, the head always uses all the nozzles to print either thechecker or inverse checker pattern. As for an upper half of the printarea shown in FIG. 14 having a depth of four pixels, a checker patternis first printed and an inverse checker pattern is then printed. As fora lower half thereof having a depth of four pixels, an inverse checkerpattern is first printed and a checker pattern is then printed. Whenthis printing procedure is discussed in conjunction with the aforesaidproblem, it is deduced that a print area in which many dots are createdduring the first pass and a few dots are created during the second pass,and a print area in which almost no dots are created during the firstpass and quite a few dots are created during the second pass appearalternately every other half of the length of a recording head. Thisphenomenon poses a problem, which will be described below, to occuralong a border between print areas during ink-jet recording.

In the ink-jet recording method, when a dot is superposed on apreviously recorded dot, the dot deposited after the previously-recordeddot in the superposed area tends to expand in the depth direction ofpaper.

FIG. 20 is a sectional view schematically showing the expansion. Apigment such as a dye contained in discharged ink is physically andchemically coupled with a recording medium. At this time, the couplingof the pigment with a recording medium P is definite. As long as thecoupling force does not differ among pigment types, the coupling of apigment I1 (crosshatched in FIG. 20) of previously-discharged ink with arecording medium is given priority and therefore mostly left on thesurface of the recording medium P. A pigment I2 (hatched in FIG. 20) ofink discharged later is hardly coupled with the recording medium P onthe surface of the recording medium P and therefore expands into therecording medium. When a reaction of ink is considered on the level offibers of the recording medium P, once fibers are coupled with the dyein ink, the fibers are more hydrophilic than they are when they are notcoupled therewith. Ink droplets shot (landed) at an area adjacent to ahighly hydrophilic area of the recording medium are liable to beattracted toward the area at which previously-discharged ink dropletsare shot.

When preceding ink droplets are fused insufficiently, that is, whenpreceding ink droplets contain more water, an area of a recording mediumat which the ink droplets are shot is more hydrophilic. More inkdroplets shot at an area adjacent to the area are therefore liable to beattracted to the previous area. When a print area in which many dots arecreated first and then a few dots are created, and a print area in whichalmost no dots are created first and then quite a few dots are createdduring the second pass appear alternately every other half of the lengthof a recording head, dots printed on the margin of the print areaadjacent to the print area at which much ink has been shot are easilyattracted, while dots printed on the margin of the print area adjacentto the print area in which little ink has been shot are hardlyattracted. Due to this difference in attraction, a high density area anda low density area are created on the border between the print areas.This results in density nonuniformity. The density nonuniformity becomesconspicuous especially in half-tone recording and has such periodicitythat density nonuniformity appears every other half of the length of arecording head.

When a specific mask is used to effect thinning-out printing, print datamay have the same periodicity as the mask. In other words, the amplitudeof density defined with the arrangement of print pixel locations andnon-print pixel locations in a mask may be consistent with the amplitudeof print data and then be resonant therewith. As a result, a dot arrayis formed to include a pattern oriented in a certain direction. Ingeneral, this phenomenon is referred to a moire pattern. When images ona plurality of lines are based on the same mask, the moire pattern ismore conspicuous and more discernible by users. The moire patterndepends largely on the periodicity of a mask.

Due to the aforesaid problems, the multi-pass printing which has beenadopted to correct differences of nozzles from one another does notalways provide satisfactory image quality because of densitynonuniformity. The density nonuniformity has such periodicity that itappears in every other print area having a certain depth. Theperiodicity facilitates human perception of discerning the densitynonuniformity.

Next, consideration will be given to printing on a type of recordingmedium that is prone to beading and less absorptive, such as transparentfilm, but not printing on a type of recording medium that is quiteabsorptive, such as coated paper or plain paper.

If an area of a recording medium, which is prone to beading even in anormal condition, is twisted, the ink beads are stopped by the whitestripe and enlarged to produce large streaky patches. This phenomenon ismore critical in transparent film than in plain paper or coated paper.In an effort to solve this problem, a proposal has been made for amethod of repeating recording a plurality of times in order to completean image for one line.

However, according to the prior art, a thinning-out mask is a fixedmask. When a thinning-out mask which may cause a great differencebetween the number of print dots for the first pass and that for thesecond pass is employed, beading often varies its intensity especiallyduring half-tone recording. That is to say, when a large number of dotsare printed during a single pass, beading becomes more intense. Theintensity of beading changes with the synchronism of a gray scalepattern with a thinning-out mask pattern for each pass. Aside from thiscase, when beading occurs between adjoining dots, a half-tone ditherpattern may be enlarged or exaggerated to become a conspicuousunpleasant pattern, or a gray scale may be destroyed.

When the conventional fixed mask for regularly thinning-out is used,beading occurs askew and appears with exaggerated askewness because ofan inaccurate mounting position of a recording head, unequal speeds of acarriage during a plurality of printing passes, different set positionsof a carriage, different paper feed positions, and differences in inkdischarging speed of a recording head. When the regularity of a fixedmask is made higher in order to eliminate the influence of beading orthe mask size thereof is made larger, if the fixed mask is displacedfrom an ideal position due to an error, beading becomes moreconspicuous. This depends on the pattern of a fixed mask, though. Theaforesaid moire pattern is therefore enlarged.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a recording apparatus,and an ink-jet recording apparatus and method that can minimizeoccurrence of density nonuniformity and offer satisfactory imagequality.

Another object of the present invention is to provide an ink-jetrecording apparatus and method capable of minimizing occurrence ofnonuniform density and offering satisfactory image quality even for atype of recording medium that is prone to beading.

Yet another object of the present invention is to provide a recordingapparatus, and an ink-jet recording apparatus and method that can effectsuccessful recording irrelevant of a record image.

To achieve the above objects, the present invention is characterized bya recording apparatus for recording using a recording head having aplurality of recording elements, comprising:

scan controlling means for controlling the recording head to scan thesame record area of a recording medium a plurality of times;

producing means for producing a plurality of random masks each having apredetermined size and defining a random array of non-record pixellocations and record pixel locations;

thinning-out means for thinning out record data using the random masksproduced by the producing means, the random masks being utilized asthinning-out masks for each record area; and

record controlling means for forming thinned-out images by recording therecord data thinned out by the thinning-out means during respectivescans and thus completing an image.

The present invention is further characterized by a recording apparatusfor recording using a recording head having a plurality of recordingelements. The apparatus comprises:

scan controlling means for controlling the recording head to scan thesame record area of a recording medium a plurality of times;

selecting means for randomly selecting a plurality of masks each havinga predetermined size and defining an array of non-record pixel locationsand record pixel locations;

thinning-out means for thinning out record data using the masks selectedby the selecting means, the randomly-selected masks being utilized asthinning-out masks for each record area; and

record controlling means for forming thinned-out images by recording therecord data thinned out by the thinning-out means, during respectivescans, and thus completing an image.

The present invention is still further characterized by a recordingapparatus for recording using a recording head having a plurality ofrecording elements. The apparatus comprises:

scan controlling means for controlling the recording head to scan thesame record area of a recording medium a plurality of times;

producing means for producing a plurality of random masks each having apredetermined size and defining a random array of non-record pixellocations and record pixel locations;

selecting means for randomly selecting a plurality of masks each havinga predetermined size and defining an array of non-record pixel locationsand record pixel locations;

synthesizing means for synthesizing the masks randomly selected by theselecting means with the random masks produced by the producing means soas to produce synthetic masks providing different thinning-out ratiosfrom the random masks;

thinning-out means for thinning out record data using the syntheticmasks produced by the synthesizing means, the synthetic masks beingutilized as thinning-out masks for each record area; and

recording controlling means for forming thinned-out images by recordingthe record data thinned out by the thinning-out means, during respectivescans, and thus completing an image.

The present invention is further characterized by a recording apparatusfor recording using a recording head having a plurality of recordingelements, comprising:

scan controlling means for controlling the recording head to scan thesame record area of a recording medium a plurality of times;

specifying means for specifying different kinds of masks, each of whichdefines an array of non-record pixel locations and record pixellocations, for use as thinning-out masks for respective record areas;

thinning-out means for thinning out record data using the differentkinds of masks specified by the specifying means; and

a record controlling means for forming thinned-out images by recordingthe record data thinned out by the thinning-out means during respectivescans and thus completing an image.

The present invention is yet further characterized by a recordingapparatus for recording using a recording head having a plurality ofrecording elements, comprising:

scan controlling means for controlling the recording head to scan thesame record area of a recording medium a plurality of times;

a creating means for creating masks each having a predetermined size anddefining an array of non-record pixel locations and record pixellocations;

expanding means for expanding the masks created by the creating means;

thinning-out means for thinning out record data using the masks expandedby the expanding means, the masks being utilized as thinning-out masksfor each record area; and

record controlling means for forming thinned-out images by recording therecord data thinned out by the thinning-out means during respectivescans and thus completing an image.

The present invention is yet further characterized by an ink-jetrecording apparatus for recording using a recording head having aplurality of ink-jet nozzles for discharging ink, the recordingapparatus being operable in a normal recording mode and a thinning-outrecording mode, comprising:

a scan controlling means for controlling the recording head to scan thesame record area of a recording medium once in the normal recordingmode, while controlling the recording head to scan the same record areaof the recording medium a plurality of times in the thinning-outrecording mode;

record controlling means for controlling complete recording of an imageby recording record data during one scan when in the normal recordingmode, and by recording thinned-out images using the created thinning-outmasks during respective scans when in the thinning-out recording mode;and

thinning-out controlling means for selecting the thinning-out recordingmode and for setting masks resulting from thinning-out based onpseudo-random numbers in the record controlling means when a recordingmedium used for recording is of a predetermined type.

The present invention is yet further characterized by a recording methodfor recording using a recording head having a plurality of recordingelements, comprising the steps of:

producing a plurality of random masks each having a predetermined sizeand defining a random array of non-record pixel locations and recordpixel locations;

thinning out record data using the random masks produced, the randommasks being utilized as thinning-out masks for each record area; and

controlling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.

The present invention is still further characterized by a recordingmethod for recording using a recording head having a plurality ofrecording elements. The method comprises the steps of:

randomly selecting a plurality of masks each having a predetermined sizeand defining an array of non-record pixel locations and record pixellocations;

thinning out record data using the masks selected in the selecting step,the random masks being utilized as thinning-out masks for each recordarea; and

controlling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.

The present invention is still further characterized by a recordingmethod for recording using a recording head having a plurality ofrecording elements, the method comprising the steps of:

producing a plurality of random masks each having a predetermined sizeand defining a random array of non-record pixel locations and recordpixel locations;

randomly selecting a plurality of prestored masks each having apredetermined size and defining an array of non-record pixel locationsand record pixel locations;

synthesizing the selected prestored masks with the produced random masksso as to produce synthetic masks providing different thinning-out ratiosfrom the random masks;

thinning out record data using the synthetic masks, the synthetic masksbeing utilized as thinning-out masks for each record area; and

controlling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.

The present invention is yet further characterized by a recording methodfor recording using a recording head having a plurality of recordingelements, comprising the steps of:

specifying different kinds of masks, each of which defines an array ofnon-record pixel locations and record pixel locations, as thinning-outmasks for respective record areas;

thinning out record data using the utilized different kinds of masks;and

controlling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.

The present invention is yet further characterized by a recording methodfor recording using a recording head having a plurality of recordingelements, comprising the steps of:

creating masks each having a predetermined size and defining an array ofnon-record pixel locations and record pixel locations;

expanding the created masks;

thinning out record data using the expanded masks, the masks beingutilized as thinning-out masks for each record area;

controlling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.

The present invention is yet further characterized by an ink-jetrecording method for recording using a recording head having a pluralityof ink-Jet nozzles for discharging ink, the recording method beingoperable in a normal recording mode and a thinning-out recording mode,comprising the steps of:

controlling the recording head to scan the same record area of arecording medium once in the normal recording mode, while controllingthe recording head to scan the same record area of the recording mediuma plurality of times in the thinning-out recording mode; and

controlling complete recording of an image by recording record dataduring one scan in the normal recording mode, and by recordingthinned-out images using created thinning-out masks during respectivescans in the thinning-out recording mode, wherein

when a recording medium used for recording is of a predetermined type,the thinning-out recording mode is selected and masks resulting fromthinning-out based on pseudo-random numbers are utilized as thethinning-out masks.

With the foregoing configurations, when an image is produced with print(record) pixels defined by random masks, the image is unaffected withthe periodicity of a thinning-out array mask. Consequently, densitynonuniformity resulting from unequal numbers of print pixels printed inthe same record area during multiple passes in conventional multi-passrecording can be suppressed because the periodicity of the densitynonuniformity is eliminated.

With the aforesaid configurations, since different masks are employedfor each print (record) area, a thinning-out array mask will not beapplied cyclically to a plurality of lines. The periodicity of densitynonuniformity is thus varied so that inherent density nonuniformitybecomes inconspicuous. Eventually, high image quality can be realized.

With the aforesaid configurations, when masks are expanded in order toequalize the numbers of print (record) pixels to be rendered duringrespective recording scans, the periodicity of a mask can be varied.Thus, density nonuniformity can be made inconspicuous and high imagequality can be realized.

With the aforesaid configurations, when a recording medium used forrecording is of a predetermined type, for example, transparent film thatis prone to beading, a thinning-out recording mode is selected and masksresulting from thinning-out based on pseudo-random numbers are used asthinning-out array masks. Any thinning-out array mask will therefore notbe applied cyclically to a plurality of lines. Furthermore, theorientation and distribution of beading are randomized so that beadingbecomes inconspicuous. Eventually, high image quality is realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A)-1(E) show creation of a random mask in the first embodimentof the present invention;

FIG. 2 shows a sequence of creating random masks and executing printingusing the masks according to the first embodiment;

FIG. 3 shows a sequence of creating random masks according to the firstembodiment;

FIG. 4 shows a sequence of selecting masks at random and executingprinting using the masks according to the second embodiment;

FIGS. 5(A)-5(G) show a plurality of masks in a storage area which aresubjected to random selection;

FIG. 6 shows a sequence of creating random masks and executing printingusing the masks according to the third embodiment;

FIG. 7 shows a random mask having m lines and n columns;

FIG. 8 shows a sequence of producing a random mask, selecting masks atrandom, and executing printing using the masks according to the fourthembodiment;

FIG. 9 is an explanatory diagram concerning creation of random fixedmasks according to the fourth embodiment;

FIG. 10 shows a sequence implemented in the fifth embodiment having amask pattern check feature;

FIGS. 11-a-11-c shows a printed state attained by an ideal ink-jetprinter;

FIGS. 12-a-12-c show a printed state attained by a conventional ink-jetprinter prone to density nonuniformity;

FIGS. 13-a-13-c and 14-a-14-c are explanatory diagrams concerningconventional division printing;

FIG. 15 shows an electric circuit for producing thinning-out masksaccording to the prior art;

FIG. 16 is a timing chart concerning heat pulses according to the priorart;

FIGS. 17, 18, and 19 show 25%-, 50%-, and 63%-thinned out datamanipulated during conventional division printing and resultant printdots;

FIG. 20 is a sectional view showing two dots being superposed on arecording medium;

FIG. 21 is an explanatory diagram showing a main unit of an ink-jetrecording apparatus to which the present invention applies;

FIG. 22 is an explanatory diagram showing a heater board;

FIG. 23 is a block diagram showing a control circuit;

FIG. 24 is a block diagram showing control circuitry;

FIG. 25 shows a configuration for explaining the flow of print data;

FIG. 26 is a block diagram showing circuit elements of a data transfercircuit according to the sixth embodiment of the present invention;

FIG. 27 shows a random mask according to the seventh embodiment;

FIG. 28 shows a recording head positioned at consecutive print areas andmasks employed according to the seventh embodiment;

FIG. 29 is a block diagram showing creation of random masks according tothe seventh embodiment;

FIG. 30 is a block diagram showing the relationships among a CPU, a ROM,and a RAM in the seventh embodiment;

FIG. 31 shows specifications of different masks for each print areaaccording to the eighth embodiment of the present invention;

FIGS. 32(A)-32(D) show examples of 4-by-4 thinning-out masks eachoffering a duty ratio of 25% in the eighth embodiment;

FIG. 33 is an explanatory diagram concerning segments of a recordinghead correspondent with print areas according to the eighth embodiment;

FIG. 34 is an explanatory diagram showing 100% furnishing using four4-by-4 masks in the eighth embodiment;

FIG. 35 shows a sequence of specifying masks for each print areaaccording to the eighth embodiment;

FIG. 36 is an explanatory diagram concerning the process of producing animage using different masks for each print area according to the eighthembodiment;

FIG. 37 shows a sequence for specifying cyclic masks according to theninth embodiment;

FIG. 38 is an explanatory diagram concerning control of periodicity of acyclic mask using a cycle value in the ninth embodiment;

FIG. 39 is an explanatory diagram concerning creation of masks using aring buffer in the tenth embodiment;

FIG. 40 is a block diagram showing circuit elements of a data transfercircuit in the eleventh embodiment of the present invention;

FIG. 41 is a timing chart showing an action of an expand counter for usein expanding masks and that of a column counter in the eleventhembodiment;

FIG. 42 is an explanatory diagram concerning expansion of four maskseach having a size of 4 by 4 dots;

FIGS. 43 and 44 show examples of results of printing data, which isthinned out at duty ratios of 50% and 62.5% respectively, using expandedmasks in the eleventh embodiment;

FIG. 45 shows a sequence of expanding masks according to the eleventhembodiment;

FIG. 46 shows a sequence of specifying a quantity of expansion for masksrelative to a duty ratio according to the twelfth embodiment;

FIG. 47 is an explanatory diagram showing specification of masks foreach print area performed as recording proceeds according to the twelfthembodiment;

FIG. 48 shows a sequence of specifying a quantity of expansion for masksrelative to a type of recording medium according to the thirteenthembodiment;

FIG. 49 is an explanatory diagram showing the occurrence of beading inthe fourteenth embodiment;

FIG. 50 shows an ink-jet value control table involving ambienthumidities in the fifteenth embodiment;

FIG. 51 shows an ink-jet value control table involving types ofrecording media in the fifteenth embodiment; and

FIG. 52 shows a change of a beading pattern resulting from a dot-by-dotvariation of a quantity of ink discharge in the sixteenth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of an ink-jet recording apparatus of the present inventionwill be described in detail with reference to the drawings.

FIGS. 21 to 25 are explanatory diagrams showing an ink jet unit IJU, anink jet head IJH, an ink tank IT, an ink jet cartridge IJC, a main unitof an ink-jet recording apparatus IJRA, and a carriage HC, and alsoshowing the relationships among these components. Using these drawings,the components will be described.

(i) Brief description of a main unit

FIG. 21 shows an example of an appearance of an ink-jet recordingapparatus IJRA to which the present invention applies. In FIG. 21, alead screw 5004 is interlocked with a drive motor 5013 via driving forcetransmission gears 5011 and 5009, and rotates with forward or reverserotation of the drive motor 5013. A carriage HC engages with a spiralgroove 5005 formed on the lead screw 5004 using a pin (not shown), andreciprocates in directions of arrows a and b. The carriage HC loads anink jet cartridge IJC. Numeral 5002 denotes a paper presser. The paperpresser 5002 presses paper to a platen 5000 while the carriage ismoving. Numerals 5007 and 5008 denote photo-couplers. The photo-couplers5007 and 5008 serve as a home-position sensing means that senses thepresence of a carriage lever 5006 interposed between the photo-couplersand changes rotating directions of the motor 5013. Numeral 5016 denotesa member for supporting a cap member 5022 for capping the front surfaceof a recording head. Numeral 5015 denotes an absorbing means forabsorbing the contents of the cap member 5022. The absorbing means 5015thus assists in recovery of the recording head by absorbing the contentsof the cap member 5022 through a cap opening 5023. Numeral 5017 denotesa cleaning blade. Numeral 5019 denotes a member for moving the cleaningblade forward and backward. The cleaning blade 5017 and member 5019 aresupported by a main unit supporting plate 5018. Needless to say, thecleaning blade 5017 need not be shaped as shown in FIG. 21. Any knowncleaning blade can also apply to this embodiment.

Reference numeral 5021 denotes a lever for use in starting recoveryabsorption. The lever 5021 moves with the movement of a cam 5020engaging with the carriage. Driving force generated by the drive motoris controlled by a known transmitting means such as a switch using aclutch.

The capping, cleaning, and recovery absorption are initiated at specificpositions due to the reaction of the lead screw 5005 against theinvasion of the carriage into the home-position area. As long as thecapping, cleaning, and recovery absorption are initiated successfullyaccording to known timing, they can be realized in any working modes inthis embodiment.

An ink jet cartridge IJC in this embodiment can accommodate a largevolume of ink. The tip of an ink jet head IJH projects slightly from thefront surface of an ink tank IT. The ink jet cartridge IJC is secured bya positioning means for the carriage HC mounted on the main unit of theink-jet recording apparatus IJRA and by an electric contact. The ink jetcartridge IJC is dismountable from the carriage HC.

(ii) Description of a construction of the ink jet unit IJU

The ink jet unit IJU is designed to effect recording using anelectro-thermal converter for generating heat energy used to cause filmboiling of ink in response to an electric signal.

(iii) Description of a heat board

FIG. 22 schematically shows a heater board 100 for a recording head inthis embodiment. Temperature control sub-heaters 8d for use incontrolling the temperature of the recording head, ink jet rows 8gincluding ink-jet main heaters for use in discharging ink, and driveelements 8h are formed on a substrate 853 so as to have positionalrelationships shown in FIG. 22. The elements are thus arranged on thesame substrate 853, which facilitates efficiency in detecting andcontrolling the temperature of the recording head. Moreover, therecording head can be made smaller in size and the manufacturingprocesses can be reduced in number. FIG. 22 also shows the location of asection 8f of a tabletop against an outer circumferential wall. Thetabletop partitions the heater board into an area filled with ink andanother area not filled with ink. Spaces along the section 8f of thetabletop against the outer circumferential wall near the ink jet heaters8d serve as common ink chambers. Grooves formed between adjoining inkjet rows 8g on the section 8f of the tabletop against the outercircumferential wall serve as ink passages.

(iv) Description of a control circuitry

Next, a control circuitry for executing control of the aforesaidcomponents in a record mode will be described with reference to theblock diagram of FIG. 23. In FIG. 23 showing a control circuit, 10denotes an interface for inputting a record signal, 11 denotes a CPU, 12denotes a program ROM for storing control programs running under thecontrol of the CPU 11 and 13 denotes a dynamic RAM for storing variousdata (record signal and record data to be supplied to the recordinghead). The dynamic RAM 13 also stores the number of print dots and thenumber of replaced recording heads. Numeral 14 denotes a gate array forcontrolling supply of record data to the recording head 18. The gatearray 14 also controls data transfer among the interface 10, CPU 11, andRAM 13. Numeral 20 denotes a carrier motor for use in transporting therecording head 18, 19 denotes a transport motor for use in transportingrecording paper, 15 denotes a head driver for driving the recording headand 16 and 17 denote motor drivers for driving the transport motor 19and carrier motor 20, respectively.

FIG. 24 is a circuit diagram showing the components shown in FIG. 23 indetail. The gate array 14 comprises a data latch 141, a segment shiftregister 142, a multiplexer (MPX) 143, a common timing generator 144,and a decoder 145. The recording head 18 is formed with a matrix ofdiodes. Driving current flows into an ink jet heater (any of H1 to H64)selected with a common signal COM and a segment signal SEG, whereby inkis heated and discharged.

The decoder 145 decodes a timing signal generated by the common timinggenerator 144 and selects any of the common signals COM1 to COM8. Thedata latch 141 latches record data read from the RAM 13 in units ofeight bits. The multiplexer 143 outputs the record data as any ofsegment signals SEG1 to SEG8 according to the contents of the segmentshift register 142. An output of the multiplexer 143 can be modified inunits of one, two, or eight bits according to the contents of the shiftregister 142, which will be described later.

The actions of the aforesaid control circuitry will be described. Whenthe interface 10 receives a record signal, the gate array 14 and CPU 11convert the record signal into record data to be printed. The motordrivers 16 and 17 are then driven, and the recording head is drivenaccording to the record data fed to the head driver 15. Thus, printingis executed.

FIG. 25 shows a configuration of a recording apparatus for explainingthe flow of record data. Record data sent from a host computer 30 isplaced in a receiving buffer 32 incorporated in the recording apparatusvia an interface 31. The receiving buffer 32 has a storage capacity ofseveral kilobytes to several tens of kilobytes. A command analyzer 33analyzes a command specified in the record data existent in thereceiving buffer 32, and sends the record data to a text buffer 34. Inthe text buffer 34, the record data is held as data for one line in anintermediate format, and appended a print position, a type ofmodification, a size, a character code, and a font address which aredefined for each character. The storage capacity of the text buffer 34differs among types of recording apparatuses. For serial printers, thetext buffer has a storage capacity of data for several lines. For pageprinters, the text buffer has a storage capacity of data for one page. Adeveloper 35 develops the record data existent in the text buffer 34 andfeeds the record data in binary representation to a print buffer 36. Thebinary data is provided as an output signal to a recording head 37.Eventually, recording is executed. In this embodiment, the binary dataplaced in the print buffer 36 is multiplied (ANDed) by mask pattern data(random mask data) which will be described later, and then sent to therecording head 37. This makes it possible to specify mask data afterchecking data existent in the print buffer 36. Depending on the type ofrecording apparatus, the text buffer may not need be included. In thiscase, the record data placed in the receiving buffer 32 is developedduring command analysis and then written in the print buffer 36.

Using an ink-jet recording apparatus having the aforesaid configuration,exemplary embodiments of the present invention will be described below.

(First Embodiment)

The first embodiment will be described in conjunction with the drawings.In an ink-jet recording apparatus of the first embodiment, thinning-outmasks that are random masks are employed.

Production of random masks will be described in conjunction with FIG. 1.This embodiment employs 4-by-4 thinning-out masks each offering a dutyratio of 25% for use in four-pass printing. In FIG. 1A, whether or notprinting is effected is specified for each pixel location in a 4-by-4mask, and the pixel locations are assigned numbers in the form of amatrix having four lines and four columns. The columns are defined ascolumn 1, column 2, column 3, and column 4 from left to right. A methodfor creating random masks in the form of the above matrix will bedescribed below.

First, any one of pixel locations 11, 21, 31, and 41 is selected forcolumn 1 at random. In this embodiment, pixel location 11 is selected.For the selection, a random number is produced to determine a pixellocation. Similarly, any one of four pixel locations is selected foreach of columns 2, 3, and 4. In due course, a thinning-out mask offeringa duty ratio 25%, mask A-1, is completed.

Next, any one of three pixel locations (pixel locations 21, 31, and 41)except pixel location 11 used in the mask A-1 is selected for column 1as shown in FIG. 1C. In this embodiment, pixel location 21 is selected.Similarly, any one of three pixel locations is selected for each ofcolumns 2, 3, and 4. Thus, a mask A-2 is completed.

Next, any one of two pixel locations is selected for each of columns 1,2, 3, and 4 as shown in FIG. 1D. Thus, a mask A-3 is produced. Finally,a mask A-4 having the remaining pixel locations set for the respectivecolumns is produced. Thus, four thinning-out random masks each offeringa duty ratio of 25% are produced.

When printing is executed using these four masks, a print area can be100% furnished with four passes. In this embodiment, 4-by-4 thinning-outmasks each offering a duty ratio of 25% are employed. The aforesaidmethod can apply to thinning-out masks each offering a duty ratio of 50%for two-pass printing or thinning-out random masks each offering a dutyratio of 12.5% for eight-pass printing. Moreover, 6-by-6 masks or 8-by-8masks can be employed. In any case, random masks can be created tofurnish a print area 100% by making the number of passes that definesthe associated printing mode.

Next, timing of creating random masks will be described. FIG. 2 shows asequence of creating random masks for four-pass printing which isexecuted by the CPU 11. This sequence is initiated when print data hascome in. When it is confirmed that print data has been transmitted, thecarriage is ramped up at step 1. A counter in the CPU is used to managethe number of produced random masks. After the carriage is ramped up,the counter is reset at step 2. Masks are then produced at step 3. Maskproduction is shown in FIG. 3.

In FIG. 3, first, information concerning masks having already beenproduced and stored for the print data is referenced at step 11. Ifmasks have already been produced, as described in conjunction with FIG.1, pixel locations except those set in the masks are selected usingrandom numbers in order to produce a random mask. Specifically, first, apixel location for column 1 is specified. Next, a pixel location foreach of columns 2, 3, and 4 is specified. Thus, a mask is created. Themask production then terminates (steps 12 to 16).

Back to the sequence in FIG. 2, a mask produced at step 4 is stored. Forstorage, a nonvolatile RAM or a memory such as the RAM 13 is employed.After storage is completed, the counter is incremented at step 5.Control is then returned to the mask production sequence. Thus, fourmasks are produced. The mask production is then terminated at step 6.The produced masks are buffered in the RAM 13 shown in FIG. 23. Herein,the produced masks (4-by-4 masks in FIG. 1) are repeatedly placed in aplurality of storage areas so that a whole print area (for example, 64columns by 1 line) will be covered with the masks.

The print data stored in the print buffer is masked (ANDed) using themasks buffered. At step 8, printing is executed based on the maskedprint data. Finally, the random masks used for printing are deleted atstep 9. Control is passed to printing for another pass.

Produced masks need not be held until a print area is 100% furnished. Amask is deleted soon after it is used for printing. However, although aprint area has not been 100% furnished, if next print data istransmitted and random mask production is executed, other masks can beproduced and stored in addition to masks being used for furnishing.

In the four-pass printing according to this embodiment, when four newrandom masks are to be produced, a nonvolatile RAM or memory shouldmerely store masks resulting from three past scans. Masks used forprinting are deleted. The total number of masks is therefore calculatedby adding up four new masks, three of four masks resulting from thefirst past recording scan, two to four masks resulting from the secondpast recording scan, and one of four masks resulting from the third pastrecording scan. Thus, the total number of masks comes to 10. Thenonvolatile RAM or memory has a storage capacity large enough to storethese masks.

As described above, according to this embodiment, the ink-jet recordingapparatus is used to perform multi-pass recording in which printing iseffected with a plurality of movements and recording scans. Herein, aplurality of random masks can be created according to the number ofrecording scans or passes. Printing of a print area can be completedusing a plurality of random masks. The random masks can be produced sothat a print area can be 100% furnished without fail. Furthermore,random masks can be produced and stored uniquely to different printareas.

Respective print areas are therefore printed using unique random masks.The periodicity of density nonuniformity in which density nonuniformityoccurs in every other print area having a certain width can beeliminated. Thus, the point does not lie in suppression of densitynonuniformity itself. Consequently, high-definition images can berecorded.

Random masks are not periodic. In theory, the random masks willtherefore not be synchronous with various dither patterns applied toprint data. If a random mask gets partly synchronous with a ditherpattern though the probability is very low, the synchronous portion isquite small and will not be identified as density nonuniformityresulting from a difference in the number of print dots by users.Furthermore, since the masks are not periodic, a moire pattern dependenton the periodicity of a mask will not occur. Thus, when random masks areemployed, periodicity of density nonuniformity can be eliminated.Eventually, high-definition images can be recorded.

(Second Embodiment)

Next, the second embodiment will be described. The second embodimentprovides a four-pass printing method in which masks are pre-set in theROM 12 or RAM 13 so that they can be selected at random for printing.

FIG. 4 shows a sequence of selecting masks at random which is executedby the CPU 11. This sequence is initiated when print data has beeninputted. When it is confirmed that print data has been transmitted, thecarriage is ramped up at step 21. When the carriage is ramped up, theCPU 11 selects a set of masks at random from a plurality of thinning-outmasks each offering a duty ratio of 25% existent in the ROM 12 or RAM13. Since the masks are designed for thinning-out at a duty ratio of25%, four masks are required to furnish a print area 100%. For randomselection, random numbers are produced to select any one from aplurality of masks. At step 23, randomly-selected masks are stored in arewritable storage area different from the one containing the pluralityof masks. The masks are buffered at step 24. The print data in the printbuffer is masked using the masks, and then printed at step 25.

FIGS. 5(A)-5(G) show exemplary masks. In FIGS. 5(A)-5(G), seven kinds ofmasks A to G are shown. These masks are pre-set in the ROM 12 or RAM 13.Alternatively, if a rewritable storage area is available, it may bepreprogrammed such that with power on, masks are created according tothe random mask production sequence presented in the first embodiment.Random masks employed need not be fixed masks. In this embodiment, sevenkinds of masks are employed. The larger the number of kinds of masks,the larger the number of options becomes available. Consequently,randomness in selecting masks increases. The masks A to G are grouped insets of four. Four masks can furnish a print area 100%.

As described above, when the ink-jet recording apparatus is used toperform multi-pass recording in which printing is effected with aplurality of movements and recording scans, unique masks can bespecified for each print area by selecting masks at random for eachprint area. The periodicity of density nonuniformity in which densitynonuniformity occurs in every other print area having a certain widthduring recording based on fixed masks can be eliminated.

(Third Embodiment)

Next, the third embodiment will be described. The third embodimentprovides a printing method using random masks each having m lines and ncolumns.

FIG. 6 shows a sequence of producing random masks which is executed bythe CPU 11. This sequence is initiated, similarly to that in the firstor second embodiment, when print data has been inputted. At step 31, itis confirmed that print data has been transmitted, and the carriage isramped up. Random masks are then created at step 32. The masks arebuffered at step 33. The print data in the print buffer is masked usingthe masks in step 33, and then printed at step 34.

FIG. 7 shows a random mask pattern having m lines and n columns. In thisembodiment, unlike the first embodiment, pixel locations are notselected column by column at random. Random numbers are used to specifypixel locations for a whole matrix composed of m lines and n columns,whereby a mask is produced. For producing thinning-out masks eachoffering a print duty ratio of 25% for four-pass printing, a probabilityof generation of random numbers is set to 1/4. All four masks may beproduced using random numbers, which, however, cannot achieve 100%furnishing. In this embodiment, therefore, the first three masks areproduced using random numbers and the fourth mask is produced so thatpixels which have not been furnished by the three masks can be printed.

This enables 100% furnishing. However, the fourth mask is a thinning-outmask for use in printing at a duty ratio of 25% or higher. The threeprevious masks have been produced using random numbers, in which thesame pixel location may be specified for printing though thisprobability is quite low. In this case, printing is therefore achievedat a duty ratio 100% or higher.

Normally, when a plurality of recording scans are performed, ink blotsor soaks into a recording medium differently from that when recording iscompleted with only one scan. Optical density tends to deteriorateslightly. In this embodiment, since masks produced at random are used,the density drop can be minimized.

As mentioned above, when the ink-jet recording apparatus is used toperform multi-pass recording in which printing is achieved with aplurality of movements and recording scans, random masks each having mlines and n columns are produced for printing. Similarly to the firstand second embodiments, periodicity of density nonuniformity can beeliminated. This embodiment is especially effective for printing usingrelatively large masks.

(Fourth Embodiment)

Next, the fourth embodiment will be described. The fourth embodimentprovides a printing method in which random masks each having m lines andn columns, which have been described in the third embodiment, are usedin combination with fixed masks selected at random, which have beendescribed in the second embodiment.

FIG. 8 shows a sequence of combining random masks and fixed masks whichis executed by the CPU 11. This embodiment adopts thinning-out maskseach offering a 25% print duty ratio for four-pass printing.

In FIG. 8, when the carriage is ramped up, a random mask having m linesand n columns is produced. The production sequence is the same as thatin the third embodiment (steps 41 and 42). However, in this embodiment,a thinning-out mask offering a 50%-duty ratio is produced. The producedrandom mask is temporarily stored in a nonvolatile RAM or a memoryrealized with the RAM 13 at step 43. With the random mask stored, atstep 44, thinning-out fixed masks each offering a 50% print duty ratioare created by executing the random mask selection mentioned in thesecond embodiment. The two kinds of masks are combined to producethinning-out masks each offering a 25%-print duty ratio. Thethinning-out masks each offering a 25%-print duty ratio are stored in anonvolatile RAM or a memory realized with the RAM 13 at step 45. Thestored random fixed masks are buffered at step 46. Print data in theprint buffer is then masked using the buffered masks, and then printedat step 47.

FIG. 9 shows the flow of producing masks. First, a random mask offeringa 50%-print duty ratio and having m lines and n columns is producedusing random numbers. This random mask is masked with two fixed maskseach offering a 50%-print duty ratio, thus producing two random maskseach offering a 25%-print duty ratio and having m lines and n columns.When a reverse pattern of the first random mask pattern offering a50%-print duty ratio and having m lines and n columns is masked with thesame fixed mask patterns, two other random masks each offering a25%-print duty ratio and having m lines and n columns are produced. Thisprocedure is not illustrated. Thus, a total of four masks are produced.

Using this embodiment, mask patterns offering different duty ratios canbe produced using two kinds of masks; a random mask and fixed masks.Moreover, random fixed masks can be produced to have the randomnesscharacteristic of random masks and the certainty characteristic of fixedmasks in offering different printing duty ratios. When mere random masksare employed, an image produced may give a slight sense of coarsenessdue to irregularity though it depends on the mask patterns. The sense ofcoarseness on an image can be suppressed by combining a random mask withfixed masks.

Instead of fixed masks, masks expanded along lines or columns may beemployed. Even this variant can suppress the sense of coarseness on animage.

(Fifth Embodiment)

Next, a pattern check feature for random masks will be described.

This embodiment includes a feature for preventing a mask produced usingrandom numbers from being synchronous with print data. FIG. 10 shows asequence executed by the CPU 11 using the pattern check feature. Thissequence is a combination of the sequence in FIG. 1 with the processingby the pattern check feature.

Only the processing performed by the pattern check feature will bedescribed and other processing will not. Pattern check is such thatimmediately after a mask is produced at step 53, before the mask isstored at step 54, it is checked if the mask is consistent with aprohibited mask which has been pre-set. If the masks are consistent witheach other, control is returned to a step of mask pattern production.Another mask is then produced. The prohibited mask is a mask liable toget synchronous with print data, such as a checker-pattern orinverse-checker pattern mask described in conjunction with FIG. 14.Thus, when a random mask is produced, the mask can offer more reliablerandomness.

(Sixth Embodiment)

FIG. 26 is a block diagram showing circuit elements of a data transfercircuit in which the present invention is implemented. In FIG. 26, 101denotes a data register connected over a memory data bus and designed totemporarily store print data read from a print buffer 130 in a memory(equivalent to the RAM 13 in FIG. 23). Numeral 102 denotes aparallel-serial converter for converting the data stored in the dataregister 101 into serial data, 103 denotes an AND gate for maskingserial data and 104 denotes a counter for use in managing the number ofdata transfers.

Reference numeral 105 denotes a register connected to a CPU 110(equivalent to the CPU 11 in FIG. 23) over a CPU data bus and designedto store masks. Numeral 106 denotes a selector for specifying a columnposition in a mask, 107 denotes a selector for specifying a lineposition in a mask and 111 denotes a counter for use in managing columnpositions.

The data transfer circuit shown in FIG. 26 transfers 128-bit print datato the recording head in a serial transfer mode in response to a printcommand signal sent from the CPU 110. Print data stored in the printbuffer 130 in the memory is temporarily stored in the data register 101and converted into serial data by the parallel-serial converter 102. Theconverted serial data is masked by the AND gate 103, and thentransferred to the recording head. The transfer counter 104 counts thenumber of transferred bits and terminates data transfer when it hascounted 128 transferred bits.

The mask register 105 consists of four mask registers A, B, C, and D,and stores masks written by the CPU 110. Each of the registers A, B, C,and D stores a mask of four bits high and four bits wide. The selector106 receives a count value of the column counter 111 as a select signaland selects mask data associated with the column position represented bythe select signal. The selector 107 receives a count value of thetransfer counter 104 as a select signal and selects mask data associatedwith the line position represented by the select signal. The AND gate103 masks transferred data using the mask data selected by the selectors106 and 107. The 4-by-4 masks stored in the registers A to D in theregister 105 are specified eight times or set in eight storage areasequivalent to a depth of 32 bits by means of the selector 106, and thenspecified repetitively or set in consecutive storage areas equivalent toone line by means of the selector 107.

In this embodiment, masked transfer data is supplied directly to therecording head. Alternatively, the masked transfer data may be placedtemporarily in the print buffer.

(Seventh Embodiment)

Next is a printing method in which random masks are specified for eachprint area and displaced for each pass.

FIG. 27 shows random masks employed in this embodiment. This embodimentemploys masks each having a data size of 2 kilobytes (4 bytes alongcolumns by 8 kilobytes along rasters). The masks are used for four-passprinting. Since the random masks in this embodiment are designed forfour-pass printing, they are dedicated to areas A, B, C, and D. The fourmasks are concatenated to produce a single mask. The random masks arerecorded in the RAM 13. Read-out positions (pointers) can be set freely.Moreover, the pointers can be displaced for each print area.

FIG. 28 shows a moving recording head and masks employed for respectiveprint areas. During the first recording scan, a mask Al is used forprinting. During the subsequent recording scans, masks B1, C1, and D1are used for printing. Thus, recording is completed. The mask Alcorresponds to a mask allocated to an area A in FIG. 27, of whichpointer points to a position 1. Similarly, the masks B1, C1, and D1correspond to masks allocated to areas B, C, and D in FIG. 27, of whichpointers point to positions 1. For the next print area, masks A2, B2,C2, and D2 are employed. The pointers of the masks A2, B2, C2, and D2point to positions displaced from those pointed to by the pointers ofthe previous masks. The displacement can be set to any value. In thisembodiment, the displacement between adjoining print areas is 256columns. The pointers return to the same positions every nine recordingscans. The masks applied to two neighboring print areas look as if theywere originated from different masks. With this mask displacement, theadvantage provided by using different masks can be gained merely bydisplacing the pointers of sub-masks forming a single mask.

Next, a random mask production sequence will be described. FIG. 29 is ablock diagram showing random mask production. This embodiment isconcerned with four-pass printing. First, a mask of a specific size iscreated and filled with the same numbers of four kinds of parameters (a,b, c, and d). Two of the parameters are exchanged with each other usingrandom numbers. This exchange is repeated a plurality of times in orderto produce a mask in which the parameters of different kinds areallocated at random. The exchange frequency can be set to any value aslong as a mask to be produced has randomness. In this embodiment, theexchange frequency is set to a product of 25000 by 15 times.

The random array mask of parameters is stored in the ROM 12. Based onthe mask, thinning-out masks are created. For example, the parameters a,b, c, and d are associated with masks A, B, C, and D. Bits positioned atthe locations of associated parameters are turned on, thus creating amask. Since the parameters are allocated at random, a created mask is arandom mask of a random array. Furthermore, since a single mask is usedto create various masks, the created random masks enable 100% furnishingwithout fail. This sequence is executed by the CPU 11. Created masks arestored in the RAM 13 for future use.

FIG. 30 shows the relationships among the CPU 11, ROM 12, and RAM 13.When a printer itself executes the above sequence, a random array ofdata is stored in the ROM 12. With power on, the aforesaid random masksare created and stored in the RAM 13 as they are. When the carriage isramped up for each recording scan, a random mask is read from the RAM13. The read random mask and print data in the print buffer are ANDedfor printing.

In creation of random masks, masks can be varied depending on printmodes. For example, the same random array of data is used to createrandom masks for two-pass printing, four-pass printing, and eight-passprinting. Applicable print modes are determined by the number of kindsof parameters used to structure the random array of data (four kinds inFIG. 29). Assuming that 24 kinds of parameters (for example, 0 to 23)are used to structure data, random masks based on the data areapplicable to print modes determined with the numbers of passescorresponding to the divisors of 24. That is to say, when a divisor 2 of24 is concerned, two random masks are created in association withparameters 0 to 11 and 12 to 23, and applicable to a print modedetermined with two passes. When a divisor 3 of 24 is concerned, threerandom masks are created in association with parameters 0 to 7, 8 to 15,and 16 to 23, and applicable to a print mode determined with threepasses. The same applies to divisors 4, 6, 8, 12 and 24.

In the above description, one parameter is associated with one mask.Alternatively, a plurality of parameters may be associated with onemask. This enables not only furnishing at 100% or higher but also doubleprinting at a certain ratio. Moreover, the furnishing ratio can beincremented at a certain rate dependent on the number of kinds ofparameters. In the above example in which 24 kinds of parameters areemployed, when two random masks are created in association withparameters 0 to 15 and 8 to 23, the furnishing ratio is 133%. When tworandom masks are created in association with parameters 0 to 17 and 6 to23, the furnishing ratio is 150%.

As described above, in this embodiment, a random array of data residingin the ROM 12 is used to create random masks. The random masks arestored in the RAM 13, and then read therefrom for printing. The read-outpositions of the random masks are displaced between respective printareas. The random masks in neighboring print areas look as if they wereoriginated from different masks. Thus, random masks can be used moreeffectively because of their asynchronism with print data.

According to the aforesaid first to seventh embodiments, a plurality ofrandom masks each defining a random array of non-print pixel locationsand print pixel locations are created, or masks are selected at random.Thinning-out masks will therefore lose periodicity. Consequently, animage produced is unaffected with the periodicity of densitynonuniformity resulting from unequal numbers of print pixels to beprinted in the same print area during several passes of conventionalmulti-pass printing. Thus, high-definition images can be produced.

(Eighth Embodiment)

Next, the eighth embodiment will be described in conjunction with thedrawings. In an ink-jet recording apparatus of the eighth embodiment,masks are specified for each print area in order to produce an image.The print area means a division in a recording scan direction of an arearecordable during one scan. In this embodiment, the area recordableduring one scan is divided into four portions.

Recording accompanied by creation of masks for each print area will bedescribed in conjunction with FIG. 31. This embodiment adopts four-passprinting in which recording of one print area is completed by performingrecording scan four times. Masks employed are 4-by-4 thinning-out maskseach offering a 25%-print duty ratio. Whether or not a pixel is printedis specified for each pixel locations in each mask. First, the firstprint area is recorded using a mask A-1 during the first recording scan.Next, the first print area is recorded using a mask A-2 during thesecond recording scan. At the same time, the second print area isrecorded using a mask B-1 different from those for the first print area.During the third recording scan, the first print area is recorded usinga mask A-3, the second print area is recorded using a mask B-2, and thethird print area is recorded using a mask C-1 different from those forthe second print area. During the fourth record scan, the first printarea is recorded using a mask A-4 and thus recording of the first printarea is completed. Similarly, recording of the second print area iscompleted with masks B-1, B-2, B-3, and B-4. Recording of the thirdprint area is completed with masks C-1, C-2, C-3, and C-4. Recording ofthe fourth print area proceeds using masks D-1, D-2, and D-3.

As mentioned above, different masks are used to record each print area.In this embodiment, four kinds of masks are employed. The same masks areshared between the first and fifth print areas, and the same masks areshared between the second and sixth print areas. Depending on the numberof kinds of masks created, print areas to be recorded using the samemasks may be located closely to each other or separated from each otherby several lines. By changing the number of kinds of masks retained, thenumber of print areas to be recorded using the same masks can becontrolled.

FIGS. 32(A)-32(D) show an example of four kinds of masks employed inthis embodiment. In FIGS. 32(A)-32(D), each mask is a 4-by-4thinning-out mask offering a 25%-print duty ratio. Masks A-1, A-2, A-3,and A-4 are grouped together for use in recording a single print area.Masks B-1, B-2, B-3, and B-4 are grouped together. Masks C-1, C-2, C-3,and C-4 are grouped together. Masks D-1, D-2, D-3, and D-4 are groupedtogether. These mask groups provide different arrays of dots to beprinted.

The recording head for which masks are set will be described inconjunction with FIG. 33. The recording head shown in FIG. 33 has aplurality of nozzles each of which can be used for printing. Thisembodiment adopts four-pass printing. The nozzles in the recording headare therefore grouped into four divided areas. The divided areas areindicated by L1, L2, L3, and L4. Different masks can be setindependently for the divided areas. For example, during the fourthrecording scan shown in FIG. 1, mask A-4 is set for divided area L4,mask B-3 is set for divided area L3, mask C-2 is set for divided areaL2, and mask D-1 is set for divided area L1. During the fifth recordingscan, mask B-4 is set for divided area L4, mask C-3 is set for dividedarea L3, mask D-2 is set for divided area L2, and mask A-1 is set fordivided area L1. Thus, different masks are set independently forrespective divided areas.

The 4-by-4 thinning-out masks each offering a 25%-print duty ratio shownin FIGS. 32(A)-32(D) can furnish a certain print area, which will bedescribed using FIG. 34. In FIG. 34, masks A-1, A-2, A-3, and A-4 areemployed. The printable pixel locations differ among four masks. A printarea is not furnished 100% until all the four masks have been applied.Any printable pixel location in one mask is not duplicated in anothermask pattern. The above relationships among four masks is true for theother mask groups. Masks used for a single print area achieve 100%furnishing but are not duplicate.

Next, the timing according to which the CPU 11 specifies masks for eachprint area will be described. FIG. 35 shows a sequence of four-passprinting. This sequence is initiated when print data has been inputted.When it is confirmed that print data has been transmitted, the carriageis ramped up. When the carriage is ramped up, masks are specified. Thecarriage is ramped up at step 71. A mask is set for divided area L1 inthe recording head at step 72. One of the examples of masks shown inFIGS. 32(A)-32(D) is selected as the mask. Similarly, a mask is set fordivided area L2 at step 73. A mask is set for divided area L3 at step74. A mask is set for divided area L4 at step 75. At step 76, the masksare buffered. At step 77, printing is executed. Control is then returnedto step 71. When masks are to be specified for a print area, the masksare selected so that the print area can be 100% furnished with printdata.

Any masks can be selected freely for a new print area or an unprintedarea. Masks may be pre-set in a storage area in the ROM 12 or the like,so that when masks are to be specified, any masks can be retrieved.Alternatively, a facility for creating masks may be installed, so thatwhen masks are to be specified, masks can be created and storedtemporarily in a nonvolatile RAM or the like for future use.

Next, a process of printing respective print areas to produce an imagewill be described in conjunction with FIG. 36. FIG. 36 shows a processof producing an image by performing recording scans during four-passprinting of this embodiment. First, the first print area is recordedwith print pixels thinned out using a specified mask during the firstrecording scan. During the second recording scan, a mask different fromthat used during the first recording scan is used to record differentprint pixels. During the third recording scan, a mask different fromthose used during the first and second recording scans is used to recorddifferent print pixels. Finally, during the fourth recording scan, amask different from those used during the previous recording scans isused to record different print pixels. Thus, recording of all the printpixels in the first print area is completed.

Recording of the second print area starts with the second recordingscan. The recording is completed by following the same steps as that ofthe first print area. However, different masks are selected. The sameapplies to the third and fourth print areas. Masks different from thoseselected for other print areas are used for recording.

As described above, according to this embodiment, when the ink-jetrecording apparatus is used to perform multi-pass recording in whichprinting is achieved with a plurality of movements and recording scans,a plurality of masks can be specified for each print area according tothe number of recording scans or passes. Different masks unique torespective print areas are used for recording. This enables control ofthe periodicity of density nonuniformity in which density nonuniformityrecurs every other print area having a certain width to be minimized.That is to say, the periodicity of density nonuniformity is controlledso that density nonuniformity will be indiscernible to human eyes.Herein, the point does not lie in suppression of density nonuniformityitself. Thus, high-definition images can be recorded.

Theoretically, even if print data gets synchronous with a mask, thesynchronism occurs only in the print area to which the mask is appliedand will not occur in the other print areas. If the cycle in which printdata becomes synchronous with a print area is, for example, several tensof lines or so long such that the synchronism is unrecognizable, densitynonuniformity will be indiscernible. Periodicities of masks may bevaried so that the masks will appear according to different cycles. Thismakes density nonuniformity indiscernible. A moire pattern resultingfrom cyclic appearance of a mask can be confined to a limited area of animage, so that it will hardly be identified. Thus, when different masksare specified for respective print areas, periodicity of densitynonuniformity can be controlled. Consequently, high-definition imagescan be recorded.

(Ninth Embodiment)

Next, the ninth embodiment will be described. The ninth embodimentprovides a four-pass printing method in which printing is achieved bycontrolling periodicities of masks specified for respective print areas.

FIG. 37 shows a sequence of controlling periodicities of masks specifiedfor respective print areas which is executed by the CPU 11. Thissequence is initiated when print data has been inputted. When it isconfirmed that print data has been transmitted, the carriage is thenramped up. When the carriage is ramped up at step 81, the CPU 11determines whether masks have already been specified. If masks have beenspecified, the masks are buffered at step 85. Printing is then executedusing the masks at step 86. If no mask has been specified, a cycle valuefor use in specifying masks is determined at step 83. The masks are thenspecified at step 84. The masks are cyclic and therefore referred to ascyclic masks.

The cyclic masks are buffered at step 85. Printing is executed using thecyclic masks at step 86. Control is then returned to step 81. In thissequence, cyclic masks can be specified for each print area. If no maskhas been specified, cyclic masks are specified at steps 83 and 84. Ifmasks have already been specified, control skips from step 82 to aprinting step.

Examples of the masks are the seven kinds of masks A to G shown in FIGS.5(A)-5(G). The masks are pre-set in the ROM 12 or RAM 13. Alternatively,if a rewritable storage area is available, it may be preprogrammed thata plurality of masks are created when power is turned on. In thisembodiment, seven kinds of masks are employed. The larger the number ofkinds of masks, the larger the number of options. Consequently, therandomness in selecting masks gets higher. The masks A to G are groupedin fours. Every four of the masks A to G can realize 100% furnishing.

FIG. 38 shows reorganization of cyclic masks resulting from a change incycle value. With cycle 1, the masks A to G are specified sequentially.This is regarded as a reference cycle. With cycle 2, the masks A to Gare specified alternately. With cycle 3, the masks A to G are specifiedso that every third mask will be selected. With cycle 4, the masks A toG are specified so that every fourth mask will be selected. By changingcycle values, the order of the masks A to G can be varied. With this inmind, when cyclic masks are specified according to the sequence of FIG.7, the periodicities of cyclic masks to be specified can be controlledby designating a cycle value.

As described above, when the ink-jet recording apparatus is used toperform multi-pass recording in which printing is achieved with aplurality of movements and record scans, the periodicities of masks tobe specified uniquely to each print areas are controlled. Periodicity ofdensity nonuniformity can thus be controlled.

(Tenth Embodiment)

Next, the tenth embodiment will be described. The tenth embodimentprovides a printing method in which masks are placed in a single ringbuffer.

FIG. 39 shows a ring buffer. The ring buffer is a cyclic storage area,wherein after buffer 1, buffer 2, buffer 3, and buffer 4 are used inthat order, the buffer 1 is reused. In this embodiment, a single mask isstored in this ring buffer. When masks are needed, the buffered mask isread out from a different position. Thus, masks created based on thebuffered mask look as if they were retrieved independently.

The ring buffer shown in FIG. 39 is four bytes deep (associated with 32nozzles), so that it can be employed for four-pass printing using therecording head having 128 nozzles. The size, depth by width, of the ringbuffer depends on the configuration of the recording apparatus. In thisembodiment, the size of the ring buffer is determined to provide astorage capacity of several kilobytes. The buffer 1, buffer 2, buffer 3,and buffer 4 contain masks which permit 100% furnishing. The four masksare concatenated to form a large mask. For a print area, the mask isread from read-out positions A, B, C, and D that are the leadingaddresses of the buffers in FIG. 39. Thus, masks permitting 100%furnishing can be created. For another print area, the read-outpositions of the mask are displaced. Thus, masks can be created as ifthey were retrieved from the buffer independently. The read-outpositions A, B, C, and D are thus displaced by two columns to A', B',C', and D'.

As mentioned above, a single mask is placed in the ring buffer in thisembodiment, and the read-out positions of the mask are displaced fromprint area to print area. Thus, various masks can be specified forrespective print areas. When the ring buffer has a larger storagecapacity, masks to be specified for respective print areas loseperiodicity.

A circuitry for data transfer in the aforesaid embodiments 8 to 10 isfound in FIG. 26. Another sequence of specifying different masks forrespective print areas has been described in conjunction with FIGS. 27to 30.

According to the aforesaid embodiments 8 to 10, masks each havingnon-print pixel locations and print pixel locations arrayed arespecified uniquely for each print area. This exerts an effect of varyingperiodicities of thinning-out masks. Thus, the periodicity of densitynonuniformity resulting from unequal numbers of print pixels to beprinted in the same print area during several passes of conventionalmulti-pass recording is varied so that density nonuniformity will beinconspicuous in a produced image. Consequently, high-definition imagescan be produced.

(Eleventh Embodiment)

Next, the eleventh embodiment will be described. In the eleventhembodiment, when the ink-jet recording apparatus is used to produce animage, masks are expanded.

FIG. 40 is a block diagram showing circuit elements of a data transfercircuit in which the present invention is implemented. Circuit elementsidentical to those in FIG. 26 (sixth embodiment) are assigned the samereference numerals, of which description will be omitted.

Reference numeral 108 denotes a register connected over the CPU data busand used to determine a quantity of expansion, 109 denotes a counter forcounting the number of expansions, 112 denotes a comparator forcomparing a value set in the expand value register 108 and a value setin the expand counter 109 and 111 denotes a counter for use in managinga column position.

The expand value register 108 is a 4-bit register for storing a quantityof expansion written by the CPU 110. In the expand value register 108, 1to 16 can be set as quantities of expansion. The expand counter 109increments a count value at every receipt of a print command signal sentfrom the CPU 110. The comparator 112 compares a value in the expandvalue register 108 and a value in the expand counter 109. If the valuesagree with each other, the expand counter 109 is cleared to zeros andthe value in the column counter 111 is incremented. The column counter111 is a 2-bit counter and counts up from 0 to 3 repetitively.

FIG. 41 is a timing chart showing the actions of the expand counter 109and column counter 111. The expand counter 109 increments a count valueat every receipt of a print command signal sent from the CPU 110. If avalue in the expand counter 109 agrees with a value n in the expandvalue register, the expand counter 109 is cleared to zeros. The columncounter 111 increments a count value by one. The count value in thecolumn counter 111 is reset to zero when it comes to 3.

FIG. 42 shows setting of masks in the mask registers A, B, C, and D.Each mask is four dots deep and four dots wide. Black dots in FIG. 42indicate that the pixel locations are not masked. White dots thereinindicate that the pixel locations are masked. During print datatransfer, print data for pixels corresponding to the black dots aretransferred to the recording head as they are, and therefore printed inthe form of a bit pattern in the print buffer. Print data for pixelscorresponding to white dots are masked by the AND gate 103, andtherefore are not printed regardless of the contents of the printbuffer.

As described previously, a column position of a mask is determined witha value in the column counter 111. The column counter I11 shows the samevalue repeatedly by the frequency defined with a value set in the expandvalue register 108. An actual mask is therefore expanded horizontallyaccording to the value set in the expand value register 108 as shown inFIG. 42.

Next, an example of expanding masks will be described. FIG. 43 shows anexample of expanding in which expanded masks each offering a 50%-printduty ratio are used for thinning out. Numeral 410 denotes binary datahaving been buffered and arrayed. The binary data 410 is Bayer typeprint data which is used generally for binary-coded dithering. Numeral420 denotes a checker-pattern mask defining locations of pixelsprintable during the first pass, 430 denotes an inverse-checker patternmask defining locations of pixels printable during the second pass and440 and 450 denote illustrations showing pixels printed during the firstand second passes, respectively. In this embodiment, 2 is set as aquantity of expansion. Numeral 460 denotes a mask made by expanding thechecker-pattern mask, wherein locations of pixels printable during thefirst pass are defined, 470 denotes a mask made by expanding theinverse-checker pattern mask, wherein locations of pixels printableduring the second pass are defined and 480 and 490 denote illustrationsshowing pixels printed during the first and second passes, respectively.

When checker-pattern and inverse-checker pattern masks are used forrecording, printing is achieved during one pass, but not performedduring another pass. A produced image is therefore affected bydifferences in the individual nozzles. That is to say, the aforesaiddensity nonuniformity appears to deteriorate image definition. Incontrast, when masks made by expanding the checker-pattern andinverse-checker pattern masks are employed, as shown in theillustrations 480 and 490, print data is equally distributed andrecorded between the first and second passes. Thus, the influence ofdifferences of nozzles from one another can be minimized and the densitynonuniformity or any other fault can be avoided.

FIG. 44 shows an example of expanding in which data offering a62.5%-print duty ratio is printed. Print data 510 is also Bayer typebinary data. Similarly to FIG. 43, when printing is performed usingchecker-pattern and inverse-checker pattern masks, there is a greatdifference in the number of print dots between the first and secondpasses. However, when printing is performed using masks made byexpanding the checker-pattern and inverse-checker pattern masks, asshown in illustrations 580 and 590, the print data is equallydistributed and recorded between the first and second passes.

Next, the timing according to which the CPU 11 creates masks for eachprint area will be described. FIG. 45 shows a sequence to be initiatedwhen print data has been inputted. When it is confirmed that print datahas been transmitted, the carriage is ramped up. When the carriage isramped up, masks are created. The carriage is ramped up at step 91. Aquantity of expanding masks is set in the expand value register at step92. At step 93, masks are expanded by the quantity of expansion. Masksare pre-set in a storage area in the ROM 12 or the like in the recordingapparatus. The masks are retrieved for use. Various quantities ofexpansion can be set. It is therefore unnecessary to store a pluralityof masks. If only one reference set of masks are stored, a plurality ofmasks can be created by changing quantities of expansion. At step 94,the masks are placed in buffers (registers). At step 95, printing isexecuted. Control is then returned to step 91, and recording iscontinued.

As mentioned above, when a mask is synchronous with print data, the maskneed not be replaced with another one but is expanded. Merely byexpanding the mask, the synchronism with print data is canceled out.Deterioration of image definition can be prevented. Since it isunnecessary to hold many additional masks, a storage area that is largeenough to store the additional masks need not be defined in the ROM 12or the like. This is cost-effective. This embodiment has been describedin conjunction with Bayer type binary data. This embodiment will proveeffective for print data subjected to other dithering. In thisembodiment, any quantity of expanding masks can be adopted. This enablesselection of an optimal quantity of expansion. In this embodiment, amask is expanded horizontally to the recording scan direction.Alternatively, a mask may be expanded perpendicularly to the recordingscan direction. This will lead to higher expandability.

(Twelfth Embodiment)

Next, the twelfth embodiment will be described. In the twelfthembodiment, quantities of expansion are changed according to print dataand specified for respective print areas, and then printing is executed.

In this embodiment, a format of printable data is detected, and then theCPU 11 specifies an optimal quantity of expansion. FIG. 46 shows asequence of creating masks in which this embodiment is implemented.First, it is confirmed that print data has been transmitted. At step101, the carriage is ramped up. When the carriage is ramped up, masksare created. After the carriage is ramped up, the print data received ischecked for a print duty ratio X at step 102. Print data for a printarea that is recorded by one divided area of the recording head duringone scan is checked to find out a print duty ratio. At step 103, if theprint duty ratio X indicates 75% or higher, the print duty ratio for theprint area is recognized as ranging from 75 to 100%. At step 104, aquantity of expansion N1 is determined. If the print duty ratio X doesnot indicate 75% or higher, control is passed to step 105. If the printduty ratio X indicates 50% or higher, the print duty ratio for the printarea is recognized as ranging from 50 to 75%. At step 106, a quantity ofexpansion N2 is determined. If the print duty ratio X does not indicate50% or higher, control is passed to step 107. If the print duty ratio Xindicates 25% or higher, the print duty ratio for the print area isrecognized as ranging from 25 to 50%. At step 108, a quantity ofexpansion N3 is determined. If the print duty ratio X does not indicate25% or higher, the print duty ratio for the print area is recognized asranging from 0 to 25%. At step 109, a quantity of expansion N4 isdetermined.

At step 110, masks are expanded by the quantity of expansion determinedrelative to the print duty ratio. The masks are pre-set in a storagearea in the ROM 12 or the like in the recording apparatus. When needed,the masks are retrieved for use. At step 111, the masks are then placedin the buffers (registers) associated with print areas. At step 112,printing is executed. Control is then returned to step 101. Recording iscontinued. Thus, a quantity of expansion can be determined relative to aprint duty ratio for a print area.

Specification of masks for each print area performed as recordingproceeds will be described in conjunction with FIG. 47. This embodimentadopts four-pass printing in which recording of a print area iscompleted with four recording scans. Masks employed are thinning-outmasks each offering a 25%-print duty ratio. Whether or not a pixel is tobe printed is specified for each print pixel location in each mask.Masks expanded by a quantity of expansion associated with the 25%-printduty ratio are regarded as masks A-1, A-2, A-3, and A-4. Masks expandedby a quantity of expansion associated with a print duty ranging from 25to 50% are regarded as masks B-1, B-2, B-3, and B-4. Masks expanded by aquantity of expansion associated with a print duty ratio ranging from 50to 75% are regarded as masks C-1, C-2, C-3, and C-4. Masks expanded by aquantity of expansion associated with a print duty ratio ranging from 75to 100% are regarded as masks D-1, D-2, D-3, and D-4. Thus, a set ofthinning-out masks each offering a 25%-print duty ratio are expanded tocreate many masks.

First, the first print area is recorded using mask A-1 during the firstrecording scan. Next, during the second recording scan, the first printarea is recorded using mask A-2 and the second print area is recordedusing mask B-1 different from that for the first print area. During thethird recording scan, the first print area is recorded using mask A-3,the second print area is recorded using mask B-2, and the third printarea recorded using mask C-1 different from those for the first andsecond print areas. During the fourth recording scan, the first printarea is recorded using mask A-4. Thus, recording of the first print areais completed. Similarly, recording of the second print area is completedwith masks B-1, B-2, B-3, and B-4. Recording of the third print area iscompleted with masks C-1, C-2, C-3, and C-4. Recording of the fourthprint area proceeds using masks A-1, A-2, and A-3. Thus, each print areais recorded using masks expanded relative to a print duty ratio for theprint area.

This embodiment provides an example of specifying four quantities ofexpansion. The same quantity of expansion is specified for the first andfourth print areas. The same masks are therefore shared between thefirst and fourth print areas. The same quantity of expansion isspecified for the third and sixth print areas. The same masks aretherefore shared between the third print and sixth print areas. Theprint areas between which the same masks are shared are determineddepending on the number of kinds of masks. Thus, recording can beperformed by expanding masks relative to a print duty ratio for eachprint area.

The recording head for which masks are set has the same construction asthat described in conjunction with FIG. 31. Divided areas in therecording head are regarded as divided areas L1, L2, L3, and L4, forwhich different masks are set. For example, for the fourth recordingscan in FIG. 47, mask A-4 is set for divided area L4, mask B-3 is setfor divided area L3, mask C-2 is set for divided area L2, and mask A-1is set for divided area L1. For the fifth recording scan, mask B-4 isset for divided area L4, mask C-3 is set for divided area L3, mask A-2is set for divided area L2, and mask D-1 is set for divided area L1.Thus, different expanded masks are set uniquely for respective dividedareas.

As described above, masks can be expanded according to a print dutyratio for each print area and set independently for respective dividedareas. Masks can be expanded optimally to print data. In thisembodiment, a print duty ratio of print data is checked. When it comesto character data, after character data is identified, a quantity ofexpansion may be set uniquely.

(Thirteenth Embodiment)

Next, the thirteenth embodiment will be described. In the thirteenthembodiment, a quantity of expanding masks is determined according to atype of recording medium.

In this embodiment, a type of recording medium is recognized byanalyzing information entered by a user. A quantity of expanding masksis then determined. For enabling a user to enter information, a buttonor switch for use in designating a type of recording medium may beinstalled in the recording apparatus so that a user himself or herselfcan designate a type of recording medium. Alternatively, a feature fordetermining a type of recording medium may be incorporated in a printerdriver so that a user can designate a type of recording medium through ascreen on a host computer.

FIG. 48 shows a control sequence for creating masks in which thisembodiment is implemented. Three types of recording media, that is,plain paper, coated paper, and OHP paper, can be used selectively.First, it is confirmed that print data has been transmitted, and thenthe carriage is ramped up. When the carriage is ramped up at step 121,masks are created. After the carriage is ramped up, a type of recordingmedium loaded is identified at step 122. Depending on the type ofrecording medium, a quantity of expanding masks is placed in the expandvalue register at step 123, 124, or 125. The quantities of expansion canbe set to any values according to the properties of recording media.

As long as coated paper is concerned, since shot ink droplets quicklypermeate into the superficial layer of the coated paper, dots to berecorded at one time should preferably be distributed and not becongested. A quantity of expansion NC is set to 1 or 2. As for plainpaper, ink does not permeate into plain paper as quickly as it does intocoated paper. Ink stays in the surface of plain paper and permeatesthereunto slowly. Some adjoining ink droplets can be shotsimultaneously. A quantity of expansion NP is therefore set to any of 2to 4. When it comes to OHP paper, ink does not fuse until it dries up onthe surface of OHP paper. It therefore takes much time for ink to fuse.This means that ink stays on the surface of OHP paper for a prolongedperiod of time. Dots are easily affected with the manner of printingadjoining dots. In order to prevent occurrence of a seam or any otherdrawback in an image, some adjoining ink droplets should preferably beejected simultaneously in the form of a bolus so that the ink will notflow into other areas. A quantity of expansion, NO, is set to any of 3to 5. A plurality of adjoining ink droplets are shot simultaneously inthe form of a bolus so that the ink droplets will be attracted to oneanother. Thus, the quantities of expansion are determined based on theproperties of the recording media.

Next, masks are expanded by the set quantity of expansion at step 126.The masks are pre-set in a storage area in the ROM 12 or the like in therecording apparatus and retrieved for use. At step 127, the masks areplaced in buffers (registers). At step 128, printing is executed.Control is then returned to step 121. Recording is continued.

As described above, when a means for identifying a type of recordingmedium is included, a recording apparatus can identify a type ofrecording medium by analyzing data entered by a user, and set an optimalquantity of expansion for the type of recording medium. In thisembodiment, reaction of ink against the surface of a recording medium istaken into consideration in predetermining quantities of expansion. Thereaction of ink depends largely on a property of ink or printingenvironments. It is therefore preferable to predetermine quantities ofexpansion according to the property of ink. When a feature for sensingprinting environments such as temperature and humidity is used incombination with this embodiment, the advantage of this embodiment willbe intensified. The feature for determining a quantity of expansionaccording to print data, which has been described in the twelfthembodiment, may be used in combination with this embodiment. Thus, theadvantage of this embodiment will also be intensified so that masks canbe expanded more properly.

According to the aforesaid embodiments 11 to 13, masks each defining anarray of non-print pixel locations and print pixel locations areexpanded. This exerts an effect of varying the periodicities of masks.Density nonuniformity resulting from unequal numbers of print pixels tobe printed in the same print area during several passes of conventionalmulti-pass recording can therefore be prevented from occurring in aproduced image. According to the aforesaid embodiment, high-definitionimages can be produced. Furthermore, a plurality of sets of masks neednot be stored. Thus, cost-effectiveness can be improved.

The aforesaid embodiments 1 to 13 are not limited to ink-jet recordingbut may apply to all recording methods including heat sensitiverecording, thermal transfer recording, and wire-dot recording. Next, anadvantage gained when random masks are used for a serial printer or whenmasks are specified for each print area will be described.

Division (multi-pass) recording has been described previously, wherein aplurality of different recording elements are used to print data for oneraster so that the differences in property (causing a twist or a dotsize) among the recording elements are averaged in order to make densitynonuniformity in one print area indiscernible. This advantage ofdivision recording is hardly exerted within a single raster when printdata gets synchronous with a mask in many recording elements. In orderto destroy the synchronism with data, random masks or masks that differfrom print area to print area are used. Consequently, division printingcan be achieved effectively.

What is described above is true for all types of dot-matrix printers.When binary data representing the on and off states of recordingelements responsible for dots are used to render a pseudo-gray scale,the recording elements must be controlled to be consistent with oneanother in terms of properties. In this case, division printing usingrandom masks or division printing in which different masks are specifiedfor respective print areas will prove effective.

For a recording apparatus using heat for printing (thermal transferrecording apparatus), division printing is effective because it helpssuppress a temperature rise in a recording head. Even in this case, atemperature rise is concentrated at part of the recording headcorresponding to a portion of a thinning-out mask synchronous with printdata. Density nonuniformity (unequal dot diameters) occurs in line withthe thermal distribution in the recording head. Division recording usingrandom masks or division recording in which different masks arespecified for respective print areas will prove effective in overcomingthe above drawback.

In a color recording apparatus in which a plurality of recording headsare lined up in the scanning direction of a carriage, a tone variesdepending on the printing order of dots. The synchronism between printdata and a thinning-out mask is reflected on a tone. This results inrecording of an image whose tone is different from the one a user wantsto express. For example, as long as thermal transfer recording isconcerned, if previously-printed dots (ink layer) are present in arecording medium, dots to be transferred succeedingly are hardlytransferred. On the other hand, when it comes to ink-jet recording, ifhighly-permeable ink is employed, the dye of previously-discharged inkis absorbed into an ink hold layer of a recording medium or fibersthereof, and the dye of ink shot succeedingly is hardly absorbed. Thetone of dots printed previously is therefore intensified. Whenless-permeable ink is employed, the dye of ink discharged succeedinglydoes not flow out but accumulates on the previous layer. The tone ofdots printed succeedingly is therefore intensified. Division recordingusing random masks or division recording in which different masks arespecified for respective print areas will effectively cope with theabove phenomena, in other words, will suppress inharmonious tones from amacroscopical viewpoint.

(Fourteenth Embodiment)

Next, the fourteenth embodiment will be described in conjunction withthe drawings. In the fourteenth embodiment, pseudo-random numbers areused in a print mode designed for transparent film.

When the use of transparent film is designated, a multi-pass print modeusing masks containing pseudo-random numbers is selected automatically.This helps minimize occurrence of beading. Even if beading occurs, theorientation of beading is not dependent on the presence of afixed-pattern mask or twist which is oriented on a fixed basis. Theorientation of beading is randomized based on the printing order definedwith pseudo-random numbers and therefore becomes inconspicuous. Aprinter or any other printing apparatus usually has an error in printingprecision. Even when a shooting position is displaced from a referenceposition due to a speed of a carriage that is unequal to a referencespeed, beading is oriented at random by the quantity of displacement.This embodiment provides an actual image that is macroscopically moreuniform than an image produced by arranging regular masks with highprecision.

In this embodiment, similarly to the aforesaid eighth embodiment, masksare specified for each print area and then an image is produced.

A ring buffer described in the tenth embodiment may be employed.Alternatively, a data transfer circuit described in the sixth embodimentmay be employed. Anyhow, any of the sequences described previously maybe employed to specify different masks for respective print areas.

The printed states in this embodiment will be described in conjunctionwith FIG. 49. Pixels recorded during the first recording scan will bediscussed first. This embodiment will be described on the assumptionthat transparent film is greatly liable to be blotted with ink when aquantity of discharged ink is somewhat large. Adjoining ink dropletsdischarged simultaneously supposedly cause beading because they areabsorbed into the transparent film slowly. During the second recordingscan and thereafter, adjoining ink droplets cause beading. Beadingoccurs according to a mask containing pseudo-random numbers, wherein theorientations and shapes of beading are randomized based on pseudo-randomnumbers.

By the time printing is achieved with the third recording scan,microscopic beading is completed to some extent in the first print area.It can be seen from FIG. 49 that new beading hardly occurs. Even whendots adjoin askew, if beading has already occurred perpendicularly tothe askew direction and the ink has been absorbed almost completely,another beading does not occur or dots are printed in any other state.

With the fourth recording scan, an image for the first print area iscompleted under the same circumstance as that mentioned above. Thesecond print area is completed sequentially in the similar manner. Thethird and fourth print areas are completed using different maskscontaining pseudo-random numbers. Different beading patterns definedwith the pseudo-random numbers are produced in the respective printareas. Macroscopically, a uniform image without regularity is produced.

This embodiment has been discussed concerning 100%-solid black printing.The embodiment can also apply to half-tone printing. The advantage ofthis embodiment will be intensified in a half-tone area of an imagehaving a half-tone ratio ranging from 50 to 100% in which more adjoiningdots are printed.

(Fifteenth Embodiment)

The fourteenth embodiment puts emphasis on the occurrence of beadingbased on a mask containing pseudo-random numbers. The fifteenthembodiment provides a method of controlling the occurrence of beading.

In practice, what is commercialized under the general name oftransparent film is diverse in terms of properties. The ink absorbancediffers from film to film. Accordingly, the state of beading isdiversified. Even in the same transparent film, the state of absorptiondiffers greatly with an ambient temperature and humidity. Depending onthe ambient conditions, print masks are created with differentpseudo-random numbers and a quantity of discharged ink is varied.

FIG. 50 is a table according to which a quantity of discharged ink iscontrolled with respect to an ambient humidity which is the mostinfluential factor. FIG. 51 is a table according to which a quantity ofdischarged ink is selected according to a type of recording medium oraccording to the fusibility and beading characteristic of thetransparent film.

In principle, when the transparent film employed is less absorbent ordrying is considered to proceed more slowly under relevant ambientconditions, a smaller quantity of discharged ink is adopted. If ink ishardly absorbed and remains on the transparent film in large quantities,ink droplets discharged during different passes of multi-pass printingcause beading. The resultant beading pattern may be different from theexpected one defined with pseudo-random numbers.

A quantity of discharged ink is reduced by controlling ink-jet pulsesfor multi-pass printing. In principle, a temperature sensor and ahumidity sensor are installed in a recording apparatus so that thetemperature and humidity can be optimized. Moreover, when a switchformed on a recording apparatus or a printer driver is used to identifya type of transparent film, an optimal selection table listingquantities of discharged ink can be selected in order to provide optimalquantities of control.

In this embodiment, a quantity of discharged ink is selectedautomatically relative to an ambient temperature or humidity.Alternatively, a control mode may be preprogrammed so that a user cananalyze a state of beading and designate a quantity of discharged ink.This embodiment is concerned with the control of a quantity ofdischarged ink resulting in optimal occurrence of beading.

(Sixteenth Embodiment)

The sixteenth embodiment tackles a large difference in absorbance.Specifically, a duration of each print pass is prolonged and dot sizes(diameters) are made even using pseudo-random numbers. Dot sizesthemselves are determined with random numbers. Thus, occurrence ofbeading is further randomized by varying dot sizes. FIG. 52 shows atransition of beading patterns resulting from a variation of a quantityof discharged ink from dot to dot.

When dot sizes are randomized using random numbers, two procedures areconceivable. One of the procedures is such that dot sizes aredifferentiated by varying them for respective passes of multi-passprinting. In this procedure, a large dot size is specified for the firstpass and diminished gradually for the second pass and thereafter. Aslong as the first pass or a state in which only a small number of dotsare printed is concerned, a probability of occurrence of beading due todots created during different passes is low. A large quantity ofdischarged ink is therefore permitted. Since the dot sizes specified forthe subsequent passes are getting smaller, occurrence of beading isprevented. Herein, the print area concerned is still furnished 100%.Alternatively, dot sizes may be set at random but not set in a regularlydiminishing manner from pass to pass.

The second procedure is to randomize quantities of discharged ink forrespective nozzles from pass to pass. In this procedure, the randomnessof masks and the randomness of dot sizes are multiplied mutually. Inorder to implement this procedure, the recording head and controlcircuitry must be designed so that quantities of discharged ink can bechanged among ink-jet nozzles. It will be more effective when thisprocedure is used in combination with a procedure of controllingoccurrence of beading due to dots printed during different passes byincreasing a wait time between passes.

According to the aforesaid embodiments 14 to 16, when a recording mediumused for recording is of a predetermined type, for example, transparentfilm that is prone to beading, not only a thinning-out recording mode isselected but also masks whose pixel locations are thinned out usingpseudo-random numbers that permit higher randomness are employed asthinning-out masks. The thinning-out masks will therefore not be appliedcyclically to a plurality of lines. Moreover, when orientations anddistributions of beading are randomized, beading becomes inconspicuous.Consequently, high-quality images can be produced.

In the description of the present invention, the term "random numbers"does not have a statistical meaning but has a meaning of pseudo-randomnumbers. Any numbers that do not have regularity may be employed as longas the advantages of the present invention can be provided fully.Printing or recording according to the present invention is notrestricted to production of images or the like but also applies tocreation of some patterns.

The present invention is particularly suitably usable in an ink-jetrecording head and recording apparatus, wherein thermal energy by anelectrothermal transducer, laser beam or the like is used to cause achange of state of the ink to eject or discharge the ink. This isbecause the high density of the picture elements and the high resolutionof the recording are possible. The typical structure and the operationalprinciple are preferably the ones disclosed in U.S. Pat. Nos. 4,723,129and 4,740,796. The principle and structure are applicable to a so-calledon-demand type recording system and a continuous type recording system.Particularly, however, it is suitable for the on-demand type because theprinciple is such that at least one driving signal is applied to anelectrothermal transducer disposed on a liquid (ink) retaining sheet orliquid passage, the driving signal being enough to provide such a quicktemperature rise beyond a departure from nucleation boiling point, bywhich the thermal energy is provided by the electrothermal transducer toproduce film boiling on the heating portion of the recording head,whereby a bubble can be formed in the liquid (ink) corresponding to eachof the driving signals. By the production, development and contractionof the bubble, the liquid (ink) is ejected through an ejection outlet toproduce at least one droplet. The driving signal is preferably in theform of a pulse, because the development and contraction of the bubblecan be effected instantaneously, and therefore, the liquid (ink) isejected with quick response. The driving signal in the form of the pulseis preferably such as disclosed in U.S. Pat. Nos. 4,463,359 and4,345,262. In addition, the temperature increasing rate of the heatingsurface is preferably such as disclosed in U.S. Pat. No. 4,313,124. Thestructure of the recording head may be as shown in U.S. Pat. Nos.4,558,333 and 4,459,600, wherein the heating portion is disposed at abent portion, as well as the structure of the combination of theejection outlet, liquid passage and the electrothermal transducer asdisclosed in the above-mentioned patents. In addition, the presentinvention is applicable to the structure disclosed in Japanese Laid-OpenPatent Application No. 123670/1984 wherein a common slit is used as theejection outlet for plural electrothermal transducers, and to thestructure disclosed in Japanese Laid-Open Patent Application No.138461/1984 wherein an opening for absorbing pressure waves of thethermal energy is formed corresponding to the ejecting portion. This isbecause the present invention is effective to perform the recordingoperation with certainty and at high efficiency irrespective of the typeof the recording head.

The present invention is effectively applicable to a so-called full-linetype recording head having a length corresponding to the maximumrecording width. Such a recording head may comprise a single recordinghead and plural recording heads combined to cover the maximum width.

In addition, the present invention is applicable to a serial typerecording head wherein the recording head is fixed on the main assembly,to a replaceable chip type recording head which is connectedelectrically with the main apparatus and can be supplied with the inkwhen it is mounted in the main assembly, or to a cartridge typerecording head having an integral ink container.

The provisions of the recovery means and/or the auxiliary means for thepreliminary operation are preferable, because they can further stabilizethe effects of the present invention. As for such means, there arecapping means for the recording head, cleaning means therefor, pressingor suction means, preliminary heating means which may be theelectrothermal transducer, an additional heating element or acombination thereof. Also, means for effecting preliminary ejection (notfor the recording operation) can stabilize the recording operation.

As regards the variation of the recording head mountable, it may be asingle head corresponding to a single color ink, or may be plural headscorresponding to a plurality of ink materials having different recordingcolors or densities. The present invention is effectively applicable toan apparatus having at least one of a monochromatic mode for recordingmainly with black, a multi-color mode for recording with different colorink materials and/or a full-color mode for recording with a mixture ofthe colors, which may use an integrally formed recording unit or acombination of plural recording heads.

Furthermore, in the forgoing embodiment, the ink has been liquid. It maybe, however, a ink material which is solidified below the roomtemperature but liquefied at the room temperature. Since the ink iscontrolled to be within the temperature not lower than 30° C. and nothigher than 70° C. to stabilize the viscosity of the ink to provide thestabilized ejection in usual recording apparatuses of this type, the inkmay be such that it is liquid within the temperature range when therecording signal is applied. However, the present invention isapplicable to other types of ink. In one type, a temperature rise due tothe thermal energy is positively prevented by consuming the thermalenergy for the state change of the ink from the solid state to theliquid state. Another ink material is solidified when it is left unused,to prevent the evaporation of the ink. In either of the cases, upon theapplication of the recording signal producing thermal energy, the ink isliquefied, and the liquefied ink may be ejected. Another ink materialmay start to solidify at the time when it reaches the recordingmaterial. The present invention is also applicable to such an inkmaterial that is liquefied by the application of the thermal energy.Such an ink material may be retained as a liquid or solid material inthrough holes or recesses formed in a porous sheet as disclosed inJapanese Laid-Open Patent Application No. 56847/1979 and JapaneseLaid-Open Patent Application No. 71260/1985. The sheet is faced to theelectrothermal transducers. The most effective system for the inkmaterials described above is the film boiling system.

The ink jet recording apparatus may be used as an output terminal of aninformation processing apparatus such as computer or the like, as acopying apparatus combined with an image reader or the like, or as afacsimile machine having information sending and receiving functions.

The individual components shown in outline or designated by blocks inthe drawings are all well-known in the image recording arts and theirrespective construction and operation are not critical to the operationor best mode for carrying out the invention.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

What is claimed is:
 1. A recording apparatus for recording using arecording head having a plurality of recording elements, said apparatuscomprising:scan controlling means for controlling the recording head toscan the same record area of a recording medium a plurality of times;producing means for producing a plurality of random masks, each randommask having a predetermined size and defining a random arrangement ofnon-record pixel locations and record pixel locations; thinning-outmeans for thinning out record data using said random masks produced bysaid producing means, said random masks being utilized as thinning-outmasks for each record area; and record controlling means for formingthinned-out images by printing the record data thinned out by saidthinning-out means, during respective scans, and thus completing animage.
 2. A recording apparatus according to claim 1, wherein said scancontrolling means controls the recording head to scan the same recordarea of the recording medium a plurality of times by changing dividedareas of the recording head.
 3. A recording apparatus according to claim1, further comprising storage means for storing a plurality of randommasks.
 4. A recording apparatus according to claim 1, furthercomprising:checking means for checking whether or not said random masksproduced by said producing means are consistent with a predeterminedmask; and prohibiting means for prohibiting certain random masks frombeing used as thinning-out masks when the certain random masks areconsistent with said predetermined mask.
 5. A recording apparatusaccording to claim 1, further comprising the recording head, whereinsaid recording head discharges ink from a plurality of ink-jet nozzles.6. A recording apparatus according to claim 5, wherein said recordinghead discharges the ink by way of heat.
 7. A recording apparatusaccording to claim 1, wherein said recording apparatus is incorporatedin a copying machine.
 8. A recording apparatus according to claim 1,wherein said recording apparatus is incorporated in a facsimile machine.9. A recording apparatus according to claim 1, wherein said recordingapparatus is incorporated in a computer terminal.
 10. A recordingapparatus for recording using a recording head having a plurality ofrecording elements, said apparatus comprising:scan controlling means forcontrolling the recording head to scan the same record area of arecording medium a plurality of times; selecting means for randomlyselecting a plurality of masks each having a predetermined size anddefining an arrangement of non-record pixel locations and record pixellocations; thinning-out means for thinning out record data using saidmasks selected by said selecting means, said randomly-selected masksbeing utilized as thinning-out masks for each record area; and recordcontrolling means for forming thinned-out images by recording the recorddata thinned out by said thinning-out means, during respective scans,and thus completing an image.
 11. A recording apparatus according toclaim 10, further comprising the recording head, wherein said recordinghead discharges ink from a plurality of ink-jet nozzles.
 12. A recordingapparatus according to claim 11, wherein said recording head dischargesthe ink by way of heat.
 13. A recording apparatus according to claim 10,wherein said recording apparatus is incorporated in a copying machine.14. A recording apparatus according to claim 10, wherein said recordingapparatus is incorporated in a facsimile machine.
 15. A recordingapparatus according to claim 10, wherein said recording apparatus isincorporated in a computer terminal.
 16. A recording apparatus forrecording using a recording head having a plurality of recordingelements, said apparatus comprising:scan controlling means forcontrolling the recording head to scan the same record area of arecording medium a plurality of times; producing means for producing aplurality of random masks each having a predetermined size and defininga random array of non-record pixel locations and record pixel locations;selecting means for randomly selecting a plurality of masks each havinga predetermined size and defining an array of non-record pixel locationsand record pixel locations; synthesizing means for synthesizing saidmasks randomly selected by said selecting means with said random masksproduced by said producing means so as to produce synthetic masksproviding different thinning-out ratios from said random masks;thinning-out means for thinning out record data using said syntheticmasks produced by said synthesizing means, said synthetic masks beingutilized as thinning-out masks for each record area; and recordingcontrolling means for forming thinned-out images by recording the recorddata thinned out by said thinning-out means, during respective scans,and thus completing an image.
 17. A recording apparatus according toclaim 16, further comprising the recording head, wherein said recordinghead discharges ink from a plurality of ink-jet nozzles.
 18. A recordingapparatus according to claim 17, wherein said recording head dischargesthe ink by way of heat.
 19. A recording apparatus according to claim 16,wherein said recording apparatus is incorporated in a copying machine.20. A recording apparatus according to claim 16, wherein said recordingapparatus is incorporated in a facsimile machine.
 21. A recordingapparatus according to claim 16, wherein said recording apparatus isincorporated in a computer terminal.
 22. A recording apparatus forrecording using a recording head having a plurality of recordingelements, said apparatus comprising:scan controlling means forcontrolling the recording head to scan a same record area of a pluralityof record areas of a recording medium a plurality of times; specifyingmeans for specifying a plurality of groups of different masks, eachgroup corresponding to a record area of the plurality of record areasand each of the different masks defining an arrangement of non-recordpixel locations and record pixel locations, for use as thinning-outmasks for a respective record area, wherein groups of maskscorresponding to different record areas are different from each other;thinning-out means for thinning out record data using said differentmasks specified by said specifying means; and record controlling meansfor forming thinned-out images by recording the record data thinned outby said thinning-out means, during respective scans controlled by saidscan controlling means, and thus completing an image.
 23. A recordingapparatus according to claim 22, wherein said specifying means specifiescertain ones of said masks for each record scan.
 24. A recordingapparatus according to claim 22, wherein said specifying means specifiescertain ones of said masks for respective divided areas of the recordinghead.
 25. A recording apparatus according to claim 22, wherein saidspecifying means varies periodicities in specifying said masks.
 26. Arecording apparatus according to claim 22, wherein said specifying meansproduces a plurality of complementary masks using a single mask.
 27. Arecording apparatus according to claim 22, further comprising therecording head, wherein said recording head discharges ink from aplurality of ink-jet nozzles.
 28. A recording apparatus according toclaim 27, wherein said recording head discharges the ink by way of heat.29. A recording apparatus according to claim 22, wherein said recordingapparatus is incorporated in a copying machine.
 30. A recordingapparatus according to claim 22, wherein said recording apparatus isincorporated in a facsimile machine.
 31. A recording apparatus accordingto claim 22, wherein said recording apparatus is incorporated in acomputer terminal.
 32. A recording method for recording using arecording head having a plurality of recording elements, said methodcomprising the steps of:producing a plurality of random masks eachhaving a predetermined size and defining a random arrangement ofnon-record pixel locations and record pixel locations; thinning outrecord data using the random masks produced in the producing step, therandom masks being utilized as thinning-out masks for each record area;and controlling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.
 33. A recording method according to claim 32,wherein during image forming the recording head discharges ink from aplurality of ink-jet nozzles.
 34. A recording method according to claim33, wherein the recording head discharges the ink by way of heat.
 35. Arecording method for recording using a recording head having a pluralityof recording elements, said method comprising the steps of:randomlyselecting a plurality of masks each having a predetermined size anddefining an arrangement of non-record pixel locations and record pixellocations; thinning out record data using the masks selected in saidselecting step, said random masks being utilized as thinning-out masksfor each record area; and controlling the recording head to scan thesame record area of a recording medium a plurality of times, formingthinned-out images by recording thinned-out record data duringrespective scans, and thus completing an image.
 36. A recording methodaccording to claim 35, wherein during image forming the recording headdischarges ink from a plurality of ink-jet nozzles.
 37. A recordingmethod according to claim 36, wherein the recording head discharges theink by way of heat.
 38. A recording method for recording using arecording head having a plurality of recording elements, said methodcomprising the steps of:producing a plurality of random masks eachhaving a predetermined size and defining a random arrangement ofnon-record pixel locations and record pixel locations; randomlyselecting a plurality of prestored masks each having a predeterminedsize and defining an array of non-record pixel locations and recordpixel locations; synthesizing the selected prestored masks with theproduced random masks so as to produce synthetic masks providingdifferent thinning-out ratios from the random masks; thinning out recorddata using the synthetic masks, the synthetic masks being utilized asthinning-out masks for each record area; and controlling the recordinghead to scan the same record area of a recording medium a plurality oftimes, forming thinned-out images by recording thinned-out record dataduring respective scans, and thus completing an image.
 39. A recordingmethod according to claim 38, wherein during image forming the recordinghead discharges ink from a plurality of ink-jet nozzles.
 40. A recordingmethod according to claim 39, wherein the recording head discharges theink by way of heat.
 41. A recording method for recording using arecording head having a plurality of recording elements, said methodcomprising the steps of:specifying a plurality of groups of differentmasks, each group corresponding to a record area of the plurality ofrecord areas and each of the different masks defining an arrangement ofnon-record pixel locations and record pixel locations, for use asthinning-out masks for a respective record area, wherein groups of maskscorresponding to different record areas are different from each other;thinning out record data using the specified different masks; andcontrolling the recording head to scan the same record area of arecording medium a plurality of times, forming thinned-out images byrecording thinned-out record data during respective scans, and thuscompleting an image.
 42. A recording method according to claim 41,wherein during image forming the recording head discharges ink from aplurality of ink-jet nozzles.
 43. A recording method according to claim42, wherein the recording head discharges the ink by way of heat.
 44. Arecording apparatus for recording using a recording head having aplurality of recording elements, said apparatus comprising:scancontrolling means for controlling the recording head to scan a samerecord area of a plurality of record areas of a recording medium aplurality of times; specifying means for specifying different kinds ofmasks, each of which defines an arrangement of non-record pixellocations and record pixel locations, for use as thinning-out masks forrespective record areas, wherein said specifying means variesperiodicities in specifying said masks; thinning-out means for thinningout record data using said different kinds of masks specified by saidspecifying means; and record controlling means for forming thinned-outimages by recording the record data thinned out by said thinning-outmeans, during respective scans, and thus completing an image.